The Blob

by Tommy on 5/06/2017
Orange Space Blob

Orange Space Blob

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Cosmic Inflation in a Nutshell – The Asymptotic Universe

by Tommy on 2/06/2017
The Asymptotic Universe

The Asymptotic Universe

Rant alert. I did this once before – Here.

Quantum Arithmetic Disproves Cosmic Naturalness Paradigm

I’m actually getting a little tired having to go over fundamentals like this.

Start with the equation x = 1/x. x2 = 1.

That’s a tautology, but it does set the origin to x = 1 not x = 0.

Now let’s move on to two dimensions and complex numbers and set y = 1/x.

Now we have at least e, π and 2, and rescaling the unit 2 triangle to unit area we get √2.

What I do is arbitrarily set the origin of this curve to the energy level of 109 to 1016 GeV.

I call that point the big bang, baryogenesis, axion production, fa or whatever else you care to.

What it is – the nearly scale invariant, nearly globally and locally flat universe in which we live.

Again, with a finite speed of light c and Planck unit of action h, something is gonna break.

Eventually. Sooner, or later.

In our case it was sooner.

Now I know what comes later.

Update: If there is even the slightest deviation of this function from x = y = 1, it fails to describe the universe and/or mathematics. That is, x or y ≠ 0 at y or x = ∞. The ‘geometry of information’.

So it’s easy to see that the universe is highly fine tuned in a very natural way.

Quantum arithmetic comes to the rescue once again.

Falsify or verify, it’s your choice.

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Time Reversal Invariant BCS-BEC Topological Superfluids

by Tommy on 30/05/2017

Here it comes, one way or another the nutshell will be cracked.

Time-reversal invariant topological superfluids in Bose-Fermi mixtures, Jonatan Melkær Midtgaard, Zhigang Wu and G. M. Bruun (29 May 2017)

A mixed dimensional system of fermions in two layers immersed in a Bose-Einstein condensate (BEC) is shown to be a promising setup to realise topological superfluids with time-reversal symmetry (TRS). The induced interaction between the fermions mediated by the BEC gives rise to a competition between p-wave pairing within each layer and s-wave pairing between the layers. When the layers are far apart, intra-layer pairing dominates and the system forms a topological superfluid either with or without TRS. With decreasing layer separation or increasing BEC coherence length, inter-layer pairing sets in. We show that this leads either to a second order transition breaking TRS where the edge modes gradually become gapped, or to a first order transition to a topologically trivial s-wave superfluid. Our results provide a realistic roadmap for experimentally realising a topological superfluid with TRS for the first time.

What usually happens though is that you end up breaking the nutcracker.

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Quark Gluon Plasmas Via Bose-Einstein Condensates

by Tommy on 29/05/2017

Here the very hot is unified with the very cold.

From cold Fermi fluids to the hot QGP, Marcus Bluhm and Thomas Schaefer, Presented by M. Bluhm at Critical Point and Onset of Deconfinement (CPOD) 2016 (24 May 2017)

Strongly coupled quantum fluids are found in different forms, including ultracold Fermi gases or tiny droplets of extremely hot Quark-Gluon Plasma. Although the systems differ in temperature by many orders of magnitude, they exhibit a similar almost inviscid fluid dynamical behavior. In this work, we summarize some of the recent theoretical developments toward better understanding this property in cold Fermi gases at and near unitarity.

When the universe cools, energy must be extracted.

And work must be done.

Life. It’s a gas.

Very exciting.

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First Principles Intrinsic ZT=2.15 Found in an Antimonene Layer

by Tommy on 27/05/2017

Bismuthene should be even better.

Excellent Thermoelectric Performance Predicted in Two-Dimensional Buckled Antimonene: a First-Principles Study, Kai-Xuan Chen, Shu-Shen Lyu, Xiao-Ming Wang, Yuan-Xiang Fu, Yi Heng and Dong-Chuan Mo, J. Phys. Chem. C (22 May 2017), DOI:10.1021/acs.jpcc.7b03129

Nowadays, new emerging two-dimensional (2D) materials have become a hot topic in the field of theoretical physics, material science and nanotechnology engineering due to their high surface area, planar structure and quantum confinement effect. Within two-dimensional framework, we systematically concentrate on the buckled and puckered systems consisting of the VA group elements (denoted as arsenene, antimonene and bismuthene). Among these studied systems, the buckled antimonene harbors a thermoelectric figure of merit (ZT) of 2.15 at room temperature. This is probably the highest value that has ever been reported in pristine 2D materials. By simple biaxial strain engineering, the ZT can even get enhanced to 2.9 under 3% tensile strain. The enhancement mainly results from both tuning the electronic structures and reducing the thermal conductance. This work predicts a new promising candidate in thermoelectric devices, based on the fact that buckled antimonene has been lately fabricated and proved to be stable at ambient conditions.

Bring it on.

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Gravitational Axion Grand Unification of QCD With Gravity

by Tommy on 26/05/2017

The gravitational axion QCD unification magnus opus of Giorgi Dvali.

Topological Origin of Chiral Symmetry Breaking in QCD and in Gravity, Gia Dvali (17 May 2017)

We show that the assumption of non-zero topological susceptibility of the vacuum in a fermion-free version of a theory, such as gravity or QCD, suffices to conclude the following: Once N massless fermion flavors are added to the theory, they break the chiral flavor symmetry dynamically, down to a subgroup that would be anomaly-free under gauging; In both theories, the pseudo-Goldstone corresponding to axial U(1)-symmetry becomes massive; In QCD as well as in gravity the massless fermions are eliminated from the low energy spectrum of the theory. All the above conclusions are reached without making an assumption about confinement. Some key methods of our approach are: Reformulation of topological susceptibility in the language of a three-form gauge theory; Utilization of gravity in the role of a spectator interaction for the chiral anomaly-matching in QCD; Gauging chiral symmetries and matching their anomalies using the spectator Green-Schwarz type axions. Our observations suggest that breaking of chiral symmetries in QCD and in gravity can be described in unified topological language, and seemingly-disconnected phenomena, such as, the generation of eta’-meson mass in QCD and breaking of global chiral symmetry by gravity may share a secret analogy. The described phenomenon may shed a new light – via contribution of micro black holes into the gravitational topological susceptibility of the vacuum – on incompatibility between black holes and global symmetries. It appears that explicit breaking is not the sole possibility, and like QCD, gravity may break global symmetries dynamically. As an useful byproduct, matching of gravitational anomalies provides a selection tool for compositeness, eliminating possibility of massless composite fermions where standard gauge anomaly matching would allow for their existence.

And just in the nick of time too. String theory only lives on the inside of a black hole, apparently.

The microscopic quantum black holes are the fluctuating quantum spacetime topolopgy.


An awesome paper title, no?

See also:

Nambu-Goldstone Effective Theory of Information at Quantum Criticality, Gia Dvali, Andre Franca, Cesar Gomez, Nico Wintergerst, Phys. Rev. D 92, 125002 (1 December 2015), doi:10.1103/PhysRevD.92.125002

We establish a fundamental connection between quantum criticality of a many-body system, such as Bose-Einstein condensates, and its capacity of information-storage and processing. For deriving the effective theory of modes in the vicinity of the quantum critical point we develop a new method by mapping a Bose-Einstein condensate of N-particles onto a sigma model with a continuous global (pseudo)symmetry that mixes bosons of different momenta. The Bogolyubov modes of the condensate are mapped onto the Goldstone modes of the sigma model, which become gapless at the critical point. These gapless Goldstone modes are the quantum carriers of information and entropy. Analyzing their effective theory, we observe the information-processing properties strikingly similar to the ones predicted by the black hole portrait. The energy cost per qubit of information-storage vanishes in the large-N limit and the total information-storage capacity increases with N either exponentially or as a power law. The longevity of information-storage also increases with N, whereas the scrambling time in the over-critical regime is controlled by the Lyapunov exponent and scales logarithmically with N. This connection reveals that the origin of black hole information storage lies in the quantum criticality of the graviton Bose-gas, and that much simpler systems that can be manufactured in table-top experiments can exhibit very similar information-processing dynamics.

So it appears now that I have come full circle with this.

My axion adventure is now officially over.

18 months from start to finish.

Up Next: The Resistance.

Update 1: I pulled this paper off Scholar because I don’t peruse HEP on the ArXiv.

Sabine Hossenfelder just blogged this today, which led me to her Aeon article on this subject.

Black Hole Computing, Sabine Hossenfelder, Aeon (31 March 2016)

Update 2: It’s going to take me quite a while to work through this material now that I am officially interested in these subjects. To recapitulate my axion adventure now that it’s officially finally over (pending microwave gravitational cosmic QCD axion detection in new and yet to be constructed sensitive cascading microwave axion haloscopes), this all began for me in the late fall of 2015 when I was distracted from my work in condensed matter physics – by the gravitational axion.

You can review those blog posts if you are feeling especially masochistic. Basically I had this wrapped up by Christmas of 2015, but being busy with other things and with raging dark matter and dark energy wars and an acrimonious election cycle – I had other responsibilities. So this whole idea languished until the election debacle, and it wasn’t until I could definitively exclude most, if not all, of the alternatives that I was anxious enough to get something written up on the axion and to my surprise, quantum cosmology. The origin of life essay was just practice for this.

On the Nature of Bismuth (I) Iodide in the Solid State

Thomas Lee Elifritz, Spec. Sci. Tech. 17, 85 (1994)

The Quantum Initiative – Energy in the 21st Century (1 January 2015)

Quantum Astrophysics – Quantum Physics and Astrophysics (8 October 2015)

The Cosmic Evolution of Autobiogenesis (12 June 2016)

Gravitational Axions as Dark Matter (1 January 2017)

Gravitational Axions in Quantum Gravity and Cosmology (8 January 2017)

My current status is that I am extremely pleased with my five self published 2015-2017 essays, and indeed with my 1994 bismuth iodide paper, and so considering recent developments and papers on these subjects I can’t see the need to continue to write about or even cover this stuff.

So welcome to the future! It’s here now.

And that future now is past.

I’ll see you in the future.

In Stockholm Sweden.

And the Planet Mars.

Update 3: Another big distraction for six months was the CERN LHC 750 GeV resonance.

I never drank the koolaide, though, being unqualified and unworthy.

Then the rocket blew up on the launch pad.

And then there was Trump.

Lizard King

Lizard King

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Rocket Lab Electron Launcher Launches at Exactly 4:20 PM

by Tommy on 25/05/2017
Rocket Lab Electron

Rocket Lab Electron

It didn’t quite make it to orbit, but it did everything else a rocket is supposed to do.

From my understanding it was only a test.

Congratulations, New Zealand!

And thank you, Rocket Lab.

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Chemical Bonding By Electronic Symmetry Breaking

by Tommy on 24/05/2017

This is a hugely important paper for me.

The chemical bond as an emergent phenomenon, Jon C. Golden, Vinh Ho and Vassiliy Lubchenko, The Journal of Chemical Physics, Vol. 146, 174502 (23 May 2017), DOI:10.1063/1.4982707

We first argue that the covalent bond and the various closed-shell interactions can be thought of as symmetry broken versions of one and the same interaction, viz., the multi-center bond. We use specially chosen molecular units to show that the symmetry breaking is controlled by density and electronegativity variation. We show that the bond order changes with bond deformation but in a step-like fashion, regions of near constancy separated by electronic localization transitions. These will often cause displacive transitions as well so that the bond strength, order, and length are established self-consistently. We further argue on the inherent relation of the covalent, closed-shell, and multi-center interactions with ionic and metallic bonding. All of these interactions can be viewed as distinct sectors on a phase diagram with density and electronegativity variation as control variables; the ionic and covalent/secondary sectors are associated with on-site and bond-order charge density wave respectively, the metallic sectorwith an electronic fluid. While displaying a contiguity at low densities, the metallic and ionic interactions represent distinct phases separated by discontinuous transitions at sufficiently high densities. Multi-center interactions emerge as a hybrid of the metallic and ionic bond that results from spatial coexistence of delocalized and localized electrons. In the present description, the issue of the stability of a compound is that of mutual miscibility of electronic fluids with distinct degrees of electron localization, supra-atomic ordering in complex inorganic compounds comes about naturally. The notions of electronic localization advanced hereby suggest a high throughput, automated procedure for screening candidate compounds and structures with regard to stability, without the need for computationally costly geometric optimization.

This is vindication enough for me.

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University of Illinois Covers the Dark Energy Survey DECam

by Tommy on 23/05/2017
Dark Energy Survey

Dark Energy Survey

This is really a must read student newspaper article on dark matter.

University astronomers unravel the universe with dark matter, Jean Kang, The Daily Illini, The Independent Student Newspaper at the University of Illinois since 1871 (22 May 2017)

This is exactly how science promotion should be done.

You can follow this up by reading the wiki article on the Dark Energy Survey.

The Dark Energy Survey Wikipedia Page

The Dark Energy Survey Website

Discussion: How to pronounce Illini. Say Ill – Lin(e) – I … Alumni.

I also have a Latin Chinese dictionary. Haha.

Beat that if you think you can!

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Did I Really Invent Modern Quantum Cosmology? Yes I did.

by Tommy on 20/05/2017

Like the term ‘autobiogenesis’, I did do a superficial search of the term ‘quantum cosmology’ after I coined it. It turned up in the modern era by a loop quantum gravity enthusiast, a theory (hypothesis) to which I do not subscribe. But looking back further I noticed that the ArXiv also has a General Relativity – Quantum Cosmology catagory (gr-qc) which seems to have been active as far back as 2002. Searching around, it seems to have been a fallout of this paper by David Wiltshire of the University of Adelaide and Canterbury, derived from as far back as 1995.

An introduction to quantum cosmology, D.L. Wiltshire, Published in “Cosmology: the Physics of the Universe”, Eds. B. Robson, N. Visvanathan and W.S. Woolcock (World Scientific, Singapore, 1996, pp 473-531) (3 September 2003)

This is an introductory set of lecture notes on quantum cosmology, given in 1995 to an audience with interests ranging from astronomy to particle physics. Topics covered: 1. Introduction: 1.1 Quantum cosmology and quantum gravity; 1.2 A brief history of quantum cosmology. 2. Hamiltonian formulation of general relativity: 2.1 The 3+1 decomposition; 2.2 The action. 3. Quantisation: 3.1 Superspace; 3.2 Canonical quantisation; 3.3 Path integral quantisation; 3.4 Minisuperspace; 3.5 The WKB approximation; 3.6 Probability measures; 3.7 Minisuperspace for the Friedmann universe with massive scalar field. 4. Boundary Conditions: 4.1 The no-boundary proposal; 4.2 The tunneling proposal. 5. The predictions of quantum cosmology: 5.1 The period of inflation; 5.2 The origin of density perturbations; 5.3 The arrow of time.

Note: These summer school lecture notes have been available for 5 years; but are being placed on the archive to make them more easily accessible.

See also: The Masters Thesis of Michael Patrick Cooke at Imperial College London

An Introduction to Quantum Cosmology, Michael Patrick Cooke, Master Thesis, Imperial College London (24 September 2010)

So this is really ‘old school’ quantum cosmology. What I did was port over the entire bulk of the machinery of the topological quantum field theory of condensed matter physics and dumped it into cosmology. And then I used that result to rediscover the cosmic QCD axion and then firmly established it as a microwave gravitational axion using that same mathematical machinery. But certainly Wiltshire’s exposition is useful as a historical starting point for this entirely new domain of quantum cosmology which has now been officially updated to these more modern standards.

Witness – the cosmic inflation war. I also notice David Wiltshire was an early proponent of inhomogeneous structure evolution as a basis for the mimicking of aspects of dark energy.

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Improved Water Electrolysis by Catalytic Electrodes Discovered

by Tommy on 20/05/2017

Iron phosphate on nickel phosphide foam. This does make some sense.

However, this is not catalysis. Even natural pH does not evolve oxygen or hydrogen.

This is more properly described as catalytic electrolysis since it involves using DC electricity.

Highly active catalyst derived from a 3D foam of Fe(PO3)2/Ni2P for extremely efficient water oxidation, Haiqing Zhoua, Fang Yua, Jingying Sun, Ran Hea, Shuo Chena, Ching-Wu Chua and Zhifeng Rena, PNAS (21 April 2017), doi:10.1073/pnas.1701562114

The oxygen evolution reaction (OER) is a sluggish reaction with poor catalytic efficiency, which is one of the major bottlenecks in realizing water splitting, CO2 reduction, and rechargeable metal–air batteries. In particular, the commercial utilization of water electrolyzers requires an exceptional electrocatalyst that has the capacity of delivering ultra-high oxidative current densities above 500 mA/cm2 at an overpotential below 300 mV with long-term durability. Few catalysts can satisfy such strict criteria. Here we report a promising oxygen-evolving catalyst with superior catalytic performance and long-term durability; to the best of our knowledge, it is one of the most active OER catalysts reported thus far that satisfies the criteria for large-scale commercialization of water–alkali electrolyzers.

Commercial hydrogen production by electrocatalytic water splitting will benefit from the realization of more efficient and less expensive catalysts compared with noble metal catalysts, especially for the oxygen evolution reaction, which requires a current density of 500 mA/cm2 at an overpotential below 300 mV with long-term stability. Here we report a robust oxygen-evolving electrocatalyst consisting of ferrous metaphosphate on self-supported conductive nickel foam that is commercially available in large scale. We find that this catalyst, which may be associated with the in situ generated nickel–iron oxide/hydroxide and iron oxyhydroxide catalysts at the surface, yields current densities of 10 mA/cm2 at an overpotential of 177 mV, 500 mA/cm2 at only 265 mV, and 1,705 mA/cm2 at 300 mV, with high durability in alkaline electrolyte of 1 M KOH even after 10,000 cycles, representing activity enhancement by a factor of 49 in boosting water oxidation at 300 mV relative to the state-of-the-art IrO2 catalyst.

If we could make potassium phosphate somehow with this process that would be excellent.

Electrocatalytic production of potassium phosphate and nitrate was my original goal with this.

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The Cosmological Constant is Quantum Vacuum Energy Density

by Tommy on 19/05/2017

And it self gravitates.

I haven’t really been too concerned about the dark energy problem since it is outside of my area of expertise and the majority of the matter is still missing. I can only claim the known microwave (cosmic QCD gravitational) axion for Vera Rubin and Helen Quinn. However, it appears now the obvious has been quantified. Or at least mathematicalized. Let’s just say it has been formalized.

I am now officially interested.

How the huge energy of quantum vacuum gravitates to drive the slow accelerating expansion of the Universe, Qingdi Wang, Zhen Zhu and William G. Unruh, Phys. Rev. D 95, 103504 (11 May 2017), doi:10.1103/PhysRevD.95.103504

We investigate the gravitational property of the quantum vacuum by treating its large energy density predicted by quantum field theory seriously and assuming that it does gravitate to obey the equivalence principle of general relativity. We find that the quantum vacuum would gravitate differently from what people previously thought. The consequence of this difference is an accelerating universe with a small Hubble expansion rate H ∝ Λe−βG√Λ → 0 instead of the previous prediction H = √8πGρvac/3 ∝ √GΛ2 → ∞ which was unbounded, as the high energy cutoff Λ is taken to infinity. In this sense, at least the “old” cosmological constant problem would be resolved. Moreover, it gives the observed slow rate of the accelerating expansion as Λ is taken to be some large value of the order of Planck energy or higher. This result suggests that there is no necessity to introduce the cosmological constant, which is required to be fine tuned to an accuracy of 10−120, or other forms of dark energy, which are required to have peculiar negative pressure, to explain the observed accelerating expansion of the Universe.

It looks like I called this correctly at the beginning of the year. So quantum cosmology it is.

Converting quantum vacuum energy into active matter is how it is most efficiently dissipated.

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Exact Mappings of Lattice Gauge Theories Formalized

by Tommy on 19/05/2017

This reminds me of Manuel de Llano’s formalization of aspects of BCS-BOSE (BCS-BEC).

This is modern physics in action. Enjoy!

Exact Boson-Fermion Duality on a 3D Euclidean Lattice, Jing-Yuan Chen, Jun Ho Son, Chao Wang and S. Raghu (16 May 2017)

The idea of statistical transmutation plays a crucial role in descriptions of the fractional quantum Hall effect. However, a recently conjectured duality between a critical boson and a massless 2-component Dirac fermion extends this notion to gapless systems. This duality may shed light on highly non-trivial problems such as the half-filled Landau level, the superconductor-insulator transition, and surface states of strongly coupled topological insulators. Although this boson-fermion duality has undergone many consistency checks, it has remained unproven. We describe the duality in a non-perturbative fashion using an exact UV mapping of partition functions on a 3D Euclidean lattice. Our approach is purely analytic and has the advantage of being simple and exact.

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Active Matter as a Generalization of Autobiogenesis

by Tommy on 18/05/2017

It’s officially impossible for me to continue to cover nightly Arxiv breakthroughs, being engaged for the last six months as Lizard King. Maybe I can get around to them next week, but this essay was the standout of the lot, and there were a lot of them breakthroughy enough for me to report.

Active matter, Sriram Ramaswamy, To appear in the STATPHYS26 Special Issue of JSTAT (17 May 2017)

The study of systems with sustained energy uptake and dissipation at the scale of the constituent particles is an area of central interest in nonequilibrium statistical physics. Identifying such systems as a distinct category — Active Matter — unifies our understanding of autonomous collective move- ment in the living world and in some surprising inanimate imitations. In this article I present the Active Matter framework, briefly recall some early work, review our recent results on single-particle and collective behaviour, including experiments on active granular monolayers, and discuss new directions for the future.

Yup. We’re blobs. Pretty stupid looking blobs by the looks of it. Maybe we can … evolve!

Selective breeding and genetic engineering doesn’t seem to be working out for us.

The Cosmic Evolution of Autobiogenesis

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ARPES BCS-BEC Crossover Transition – Fe(1+x)Se(x)Te(1-x)

by Tommy on 17/05/2017

Grok and you shall know.

Tuning across the BCS-BEC crossover in the multiband superconductor Fe1+ySexTe1−x : An angle-resolved photoemission study, S. Rinott, K.B. Chashka A. Ribak, E. D. L. Rienks A. Taleb-Ibrahimi, P. Le Fevre, F.Bertran, M. Randeria and A.Kanigel, Science Advances 3, 4, e1602372 (21 April 2017), doi:101126/sciadv.1602372

The crossover from Bardeen-Cooper-Schrieffer (BCS) superconductivity to Bose-Einstein condensation (BEC) is difficult to realize in quantum materials because, unlike in ultracold atoms, one cannot tune the pairing interaction. We realize the BCS-BEC crossover in a nearly compensated semimetal Fe1+ySexTe1−x by tuning the Fermi energy, ϵF, via chemical doping, which permits us to systematically change Δ/ϵF from 0.16 to 0.5 were Δ is the superconducting (SC) gap. We use angle-resolved photoemission spectroscopy to measure the Fermi energy, the SC gap and characteristic changes in the SC state electronic dispersion as the system evolves from a BCS to a BEC regime. Our results raise important questions about the crossover in multiband superconductors which go beyond those addressed in the context of cold atoms.

This is how it will be done from now on.

Got any other ideas? I can think of a few.

I completely failed to predict this in 1994.

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Nanoscopic Shiba Islands for Topological Circuit Manipulation

by Tommy on 17/05/2017

This is what I wanted to do with bismuth on nickel, but this is still shocking nevertheless.

Quantized charge transport in chiral Majorana edge modes, Stephan Rachel, Eric Mascot, Sagen Cocklin, Matthias Vojta and Dirk K. Morr (15 May 2017)

Majorana fermions can be realized as quasiparticles in topological superconductors, with potential applications in topological quantum computing. Recently, lattices of magnetic adatoms deposited on the surface of s-wave superconductors – Shiba lattices – have been proposed as a new platform for topological superconductivity. These systems possess the great advantage that they are accessible via scanning-probe techniques, and thus enable the local manipulation and detection of Majorana modes. Realizing quantum bits on this basis will rely on the creation of nanoscopic Shiba lattices, so-called Shiba islands. Here, we demonstrate that the topological Majorana edge modes of such islands display universal electronic and transport properties. Most remarkably, these Majorana modes possess a quantized charge conductance that is proportional to the topological Chern number, C, and carry a supercurrent whose chirality reflects the sign of C. These results establish nanoscopic Shiba islands as promising components in future topology-based devices.

So what’s the holdup?

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Generalized Lieb-Schultz-Mattis Theorems for SPT Phases

by Tommy on 16/05/2017

I feel a major generalization ‘coming on.

Lieb-Schultz-Mattis theorems for symmetry protected topological phases, Yuan-Ming Lu, AMS 1127-81-159 (12 May 2017)

The Lieb-Schultz-Mattis (LSM) theorem and its descendants represent a class of powerful no-go theorems that rule out any short-range-entangled (SRE) symmetric ground state irrespective of the specific Hamiltonian, based only on certain microscopic inputs such as symmetries and particle filling numbers. In this work, we introduce and prove a new class of LSM-type theorems, where any symmetry-allowed SRE ground state must be a symmetry-protected topological (SPT) phase with robust gapless edge states. The key ingredient is to replace the lattice translation symmetry in usual LSM theorems by magnetic translation symmetry. These theorems provide new insights into numerical models and experimental realizations of SPT phases in interacting bosons and fermions.

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Non-Equilibrium Irreversible Thermodynamics and Uncertainty

by Tommy on 12/05/2017

I’m always looking for new ways to look at non-equilibrium and irreversible thermodynamics.

A simple proof of the thermodynamic uncertainty relation, Changbong Hyeon and Wonseok Hwang (11 May 2017)

Using Brownian motion in periodic potential V(x) tilted by a force f, we prove the thermodynamic uncertainty relation, a recently conjectured principle for statistical errors and irreversible heat dissipation in nonequilibrium steady states. According to the relation, nonequilibrium output generated from dissipative processes necessarily incurs an energetic cost or heat dissipation q, and in order to limit the output fluctuation within a relative uncertainty ϵ, at least 2kBT2 of heat must be dissipated. We show that this bound is attained not only at near-equilibrium (fV′(x)) but also at far-from-equilibrium (fV′(x)), more generally when the dissipated heat is normally distributed. Furthermore, the energetic cost is maximized near the critical force when the barrier separating the potential wells is about to vanish. Our derivation of the uncertainty relation also recognizes a new bound of nonequilibrium dissipation that the variance of dissipated heat (σ2q) increases with its mean (μq) and is greater than 2kBTμq.

Thermodynamic uncertainty certainly is a new way of looking at these subjects.

This paper is as insightful as it gets.

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Quantum Anomaly Manifestation By Dimensional Reduction

by Tommy on 12/05/2017

This is how the quantum cosmology dark matter axion nutshell will be ultimately cracked.

Anomaly Manifestation of Lieb-Schultz-Mattis Theorem and Topological Phases, Gil Young Cho and Shinsei Ryu (10 May 2017)

The Lieb-Schultz-Mattis theorem constrains the possible low-energy and long-distance behaviors of states which emerge from microscopic lattice Hamiltonians. The theorem dictates that the emergent state cannot be a trivial symmetric insulator if the filling per unit cell is not integral and if lattice translation symmetry and particle number conservation are strictly imposed. Investigating one-dimensional symmetric gapless states which are forced to be critical by the theorem, we show that the theorem, the absence of a trivial insulator phase at non-integral filling, has a very close connection to quantum anomaly. We further show that, in terms of symmetry realizations on low-energy modes, low-energy spectrum, and anomaly, the gapless states emergent from lattice Hamiltonians are equivalent to the boundary theory of the strong symmetry-protected topological phases in one-higher dimensions, where non-local translational symmetry of the lattice is encoded as some local symmetry. Once a global symmetry is realized in a non-on-site fashion, the boundary of the topological phases can be realized in a stand-alone lattice model, and the no-go theorem for the boundary is circumvented, similar to the recent discussions of the half-filled Landau level and topological insulators. Finally we extend our analysis to the higher-dimensional example, the Dirac semimetal in three spatial dimensions.

See also:

Lieb-Schultz-Mattis Theorem and its generalizations from the Perspective of the Symmetry Protected Topological phase, Chao-Ming Jian, Zhen Bi and Cenke Xu (28 April 2017)

We ask whether a local Hamiltonian with a featureless (fully gapped and nondegenerate) ground state could exist in certain quantum spin systems. We address this question by mapping the vicinity of certain quantum critical point (or gapless phase) of the d−dimensional spin system under study to the boundary of a (d+1)−dimensional bulk state, and the lattice symmetry of the spin system acts as an on-site symmetry in the field theory that describes both the selected critical point of the spin system, and the corresponding boundary state of the (d+1)−dimensional bulk. If the symmetry action of the field theory is non-anomalous, i.e. the corresponding bulk state is a trivial state instead of a bosonic symmetry protected topological (SPT) state, then a featureless ground state of the spin system is allowed; if the corresponding bulk state is indeed a nontrivial SPT state, then it likely excludes the existence of a featureless ground state of the spin system. From this perspective we identify the spin systems with SU(N) and SO(N) symmetries on one, two and three dimensional lattices that permit a featureless ground state. We also verify our conclusions by other methods, including an explicit construction of these featureless spin states.

These are long and complicated papers with lots of references, so take your time.

Nevertheless, if you persist, you will get up to speed on this.

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Superuniversal Transport Near a Quantum Critical Point

by Tommy on 12/05/2017

This paper was difficult to get through but contained a surprise at the end.

Superuniversal transport near a (2+1)-dimensional quantum critical point, Félix Rose and Nicolas Dupuis (10 May 2017)

We compute the zero-temperature conductivity in the two-dimensional quantum O(N) model using a nonperturbative functional renormalization-group approach. At the quantum critical point we find a universal conductivity σ∗/σQ (with σQ=q2/h the quantum of conductance and q the charge) in reasonable quantitative agreement with quantum Monte Carlo simulations and conformal bootstrap results. In the ordered phase the conductivity tensor is defined, when N≥3, by two independent elements, σA(ω) and σB(ω), respectively associated to O(N) rotations which do and do not change the direction of the order parameter. Whereas σA(ω→0) corresponds to the response of a superfluid (or perfect inductance), the numerical solution of the flow equations shows that limω→0σB(ω)/σQ=σ∗B/σQ is a superuniversal (i.e. N-independent) constant. These numerical results, as well as the known exact value σ∗B/σQ=π/8 in the large-N limit, allow us to conjecture that σ∗B/σQ=π/8 holds for all values of N, a result that can be understood as a consequence of gauge invariance and asymptotic freedom of the Goldstone bosons in the low-energy limit.

This is a nightmare of html formatting so you’ll just have to read the paper like I did.

It will be well worth your time if you’re interested in this kind of thing. Like I am.

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Hydrogen Ionization in Cosmic Webs Probed By Quasar Light

by Tommy on 11/05/2017
Cosmic Web Void Filament Structure

Cosmic Web Void Filament Structure

I’m reduced to science reporting by blog, press release and main stream media.

This new science publishing paradigm is even catching up to Arxiv and Scholar.

University of California Santa Barbara Press Release

Measurement of the small-scale structure of the intergalactic medium using close quasar pairs, Alberto Rorai1, Joseph F. Hennawi, Jose Oñorbe, Martin White, J. Xavier Prochaska, Girish Kulkarni, Michael Walther, Zarija Lukić and Khee-Gan Lee, Science, 356, 6336, 418-422 (28 April 2017), DOI:10.1126/science.aaf9346

Space between galaxies is filled with a tenuous gas known as the intergalactic medium (IGM). The presence of hydrogen atoms in the IGM at different redshifts imprints a series of absorption lines in the spectra of background quasars. Rorai et al. studied pairs of closely spaced quasars and quantified how similar their absorption lines are as a function of transverse separation and redshift. They thus assessed the smoothness of the IGM on relatively small scales—several times the size of a galaxy. The results constrain interactions between galaxies and the IGM, such as heating by ultraviolet photons.

The distribution of diffuse gas in the intergalactic medium (IGM) imprints a series of hydrogen absorption lines on the spectra of distant background quasars known as the Lyman-α forest. Cosmological hydrodynamical simulations predict that IGM density fluctuations are suppressed below a characteristic scale where thermal pressure balances gravity. We measured this pressure-smoothing scale by quantifying absorption correlations in a sample of close quasar pairs. We compared our measurements to hydrodynamical simulations, where pressure smoothing is determined by the integrated thermal history of the IGM. Our findings are consistent with standard models for photoionization heating by the ultraviolet radiation backgrounds that reionized the universe.

Now Julie Cohen just needs to work on writing up the actual citation to the paper.

In addition to an embedded link, I’d like the cite.

Bad Julie! Very bad Julie!

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Cuprate Mottness Melted By Laser Charge Transfer Excitation

by Tommy on 10/05/2017

SISSA comes through for me again. Is there nothing these people can’t do?

Mottness at finite doping and charge instabilities in cuprates, S. Peli, S. Dal Conte, R. Comin, N. Nembrini, A. Ronchi, P. Abrami, F. Banfi, G. Ferrini, D. Brida, S. Lupi, M. Fabrizio, A. Damascelli, M. Capone, G. Cerullo and C. Giannetti, Nature Physics (8 May 2017), doi:10.1038/nphys4112

The influence of Mott physics on the doping–temperature phase diagram of copper oxides represents a major issue that is the subject of intense theoretical and experimental efforts. Here, we investigate the ultrafast electron dynamics in prototypical single-layer Bi-based cuprates at the energy scale of the O-2p → Cu-3d charge-transfer (CT) process. We demonstrate a clear evolution of the CT excitations from incoherent and localized, as in a Mott insulator, to coherent and delocalized, as in a conventional metal. This reorganization of the high-energy degrees of freedom occurs at the critical doping pcr ≈ 0.16 irrespective of the temperature, and it can be well described by dynamical mean-field theory calculations. We argue that the onset of low-temperature charge instabilities is the low-energy manifestation of the underlying Mottness that characterizes the p < pcr region of the phase diagram. This discovery sets a new framework for theories of charge order and low-temperature phases in underdoped copper oxides.

Massimo does know how to craft a proper press release.

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Room Temperature Biexcitons in Monolayer Tungsten Disulfide

by Tommy on 9/05/2017

This is like excitons in bismuth triiodide all over again.

Room temperature observation of biexcitons in exfoliated WS2 monolayers, I. Paradisanos, S. Germanis, N. T. Pelekanos, C. Fotakis, E. Kymakis, G. Kioseoglou and E. Stratakis (8 May 2017)

Single layers of WS2 are direct gap semiconductors with high photoluminescence (PL) yield holding great promise for emerging applications in optoelectronics. The spatial confinement in a 2D monolayer together with the weak dielectric screening lead to huge binding energies for the neutral excitons as well as other excitonic complexes, such as trions and biexcitons whose binding energies scale accordingly. Here, we report on the existence of biexcitons in mechanically exfoliated WS2 flakes from 78 K up to room temperature. Performing temperature and power dependent PL measurements, we identify the biexciton emission channel through the superlinear behavior of the integrated PL intensity as a function of the excitation power density. On the contrary, neutral and charged excitons show a linear to sublinear dependence in the whole temperature range. From the energy difference between the emission channels of the biexciton and neutral exciton, a biexciton binding energy of 65 – 70 meV is determined.

I am so excited, having experienced this phenomenon earlier. Much earlier.

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Lattice QCD Topology Further Refines Axion Mass Range

by Tommy on 9/05/2017

Topology (and axion’s properties) from lattice QCD with a dynamical charm, Florian Burger, Ernst-Michael Ilgenfritz, Maria Paola Lombardo, Michael Müller-Preussker and Anton Trunin, Proceedings of Quark Matter 2017 – XXVI International Conference on Ultrarelativistic Heavy-ion Collisions, February 5-11, 2017, Chicago IL (4 May 2017)

We present results on QCD with four dynamical flavors in the temperature range 0.9 ≲ T/Tc ≲ 2. We have performed lattice simulations with Wilson fermions at maximal twist and measured the topological charge with gluonic and fermionic methods. The topological charge distribution is studied by means of its cumulants, which encode relevant properties of the QCD axion, a plausible Dark Matter candidate. The topological susceptibility measured with the fermionic method exhibits a power-law decay for T/Tc ≳ 2, with an exponent close to the one predicted by the Dilute Instanton Gas Approximation (DIGA). Close to Tc the temperature dependent effective exponent approaches the DIGA result from above, in agreement with recent analytic calculations. These results constrain the axion window, once an assumption on the fraction of axions contributing to Dark Matter is made.

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First Light at the DESY XFEL Linear Free Electron X-Ray Laser

by Tommy on 5/05/2017
DESY XFEL Linear Superconducting Free Electron Laser

DESY XFEL Linear Superconducting Free Electron Laser

I had originally proposed one of these free electron lasers for the University of Wisconsin at Madison, under the umbrella of the Wisconsin Institute of Discovery. It was a colossal failure. Not only did the UW not get a free electron laser, but then the National Science Foundation and the Department of Energy canceled the Synchrotron Radiation Center in Stoughton, and the Wisconsin Institute of Discovery turned out to be the butt of jokes. That’s so sad, John D. Wiley.

First Light -The Firepower of the Idea – Light at the Foundation Of Discovery

We’ll just have to leave it to the Europeans again I guess.

European XFEL X-Ray Free Electron Laser

But all that empty farm land in Stoughton is making WARF rich.

And big buildings means big building contracts!

You can’t expect scientists to do things.

It’s all about patents now.

And big buildings.

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Gapless Symmetry Protected Topological Matter Proposed

by Tommy on 5/05/2017

After slugging through the previous paper, this was a breath of relief.

Gapless Symmetry Protected Topological Order, Thomas Scaffidi, Daniel E. Parker and Romain Vasseur (3 May 2017)

We introduce exactly solvable gapless quantum systems in d dimensions that support symmetry protected topological (SPT) edge modes. Our construction leads to long-range entangled, critical points or phases that can be interpreted as critical condensates of domain walls “decorated” with dimension (d−1) SPT systems. Using a combination of field theory and exact lattice results, we argue that such gapless SPT systems have symmetry-protected topological edge modes that can be either gapless or symmetry-broken, leading to unusual surface critical properties. Despite the absence of a bulk gap, these edge modes are robust against arbitrary symmetry-preserving local perturbations near the edges. In two dimensions, we construct wavefunctions that can also be interpreted as unusual quantum critical points with diffusive scaling in the bulk but ballistic edge dynamics.

Here, the method of their construction is useful. And the result is … interesting.

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Topological Quantum Chemistry Becomes Predictive

by Tommy on 5/05/2017

Wallpaper Fermions and the Topological Dirac Insulator, Benjamin J. Wieder, Barry Bradlyn, Zhijun Wang, Jennifer Cano, Youngkuk Kim, Hyeong-Seok D. Kim, A. M. Rappe, C. L. Kane and B. Andrei Bernevig, Submitted on March 21, 2017 (3 May 2017)

Recent developments in the relationship between bulk topology and surface crystalline symmetries have led to the discovery of materials whose gapless surface states are protected by crystal symmetries. In fact, there exists only a very limited set of possible surface crystal symmetries, captured by the 17 “wallpaper groups.” We show that all possible crystalline insulators, symmorphic and nonsymmorphic, can be exhaustively characterized by considering these groups. In particular, the two wallpaper groups with multiple glide lines, pgg and p4g, allow for a new topological insulating phase, whose surface spectrum consists of only a single, fourfold-degenerate, true Dirac fermion. Like the surface state of a conventional topological insulator, the surface Dirac fermion in this “topological Dirac insulator” provides a theoretical exception to a fermion doubling theorem. Unlike the surface state of a conventional topological insulator, it can be gapped into topologically distinct surface regions while keeping time-reversal symmetry, allowing for networks of topological surface quantum spin Hall domain walls. We report the theoretical discovery of new topological crystalline phases in the A2B3 family of materials in SG 127, finding that Sr2Pb3 hosts this new topological surface Dirac fermion. Furthermore, (100)-strained Au2Y3 and Hg2Sr3 host related topological surface hourglass fermions. We also report the presence of this new topological hourglass phase in Ba5In2Sb6 in SG 55. For orthorhombic space groups with two glides, we catalog all possible bulk topological phases by a consideration of the allowed non-abelian Wilson loop connectivities, and we develop topological invariants for these systems. Finally, we show how in a particular limit, these crystalline phases reduce to copies of the Su-Schrieffer-Heeger model.

See also:

Topological quantum chemistry, Barry Bradlyn, L. Elcoro, Jennifer Cano, M. G. Vergniory, Zhijun Wang, C. Felser, M. I. Aroyo and B. Andrei Bernevig (6 March 2017)

The past decade’s apparent success in predicting and experimentally discovering distinct classes of topological insulators (TIs) and semimetals masks a fundamental shortcoming: out of 200,000 stoichiometric compounds extant in material databases, only several hundred of them – a set essentially of measure zero – are topologically nontrivial. Are TIs that esoteric, or does this reflect a fundamental problem with the current piecemeal approach to finding them? Two fundamental shortcomings of the current approach are: the focus on delocalized Bloch wavefunctions – rather than the local, chemical bonding in materials – and a classification scheme based on a collection of seemingly unrelated topological indices. To remedy these issues, we propose a new and complete electronic band theory that assembles the last missing piece – the link between topology and local chemical bonding – with the conventional band theory of electrons. Topological Quantum Chemistry is a description of the universal global properties of all possible band structures and materials comprised of a graph theoretical description of momentum space and a dual group theoretical description in real space. This patches together local k⋅p dispersions into distinct global groups of energy bands: we classify all the possible bands for all 230 crystal symmetry groups involving s,p or d orbitals on any of the Wyckoff positions of every space group. We show how our topological band theory sheds new light on known TIs, and demonstrate the power of our method to predict a plethora of new TIs.

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Axions as Topological Inflatons and Geometric Curvatons

by Tommy on 5/05/2017
Axion Phase Diagram

Axion Phase Diagram

Back just before the first of the year I was deep into writing up my gravitational axion hypothesis. This was precipitated by new precision observational results demonstrating their particulate nature convincingly. The debate was raging between entropic gravity and fundamental particles, and to a lesser degree a wide variety of quite unreasonable proposals, and I was trying to get something together because I knew Vera Rubin was failing and the debate was reaching truly ridiculous and embarrassing proportions. Just as I was getting started, this paper showed up on the Arxiv. I already had a profound respect for SISSA, since their astronomy was crucial to the precision astronomical debates. So I was really happy to read this paper and blogged it briefly, but over the next week I was engaged in writing up my hypothesis and simply forgot all about it.

Since this has now been published in Physical Review Letters, it’s worth reviewing it here again.

Geometric Baryogenesis from Shift Symmetry, Andrea De Simone, Takeshi Kobayashi and Stefano Liberati, Phys. Rev. Lett. 118, 131101 (27 March 2017), doi:10.1103/PhysRevLett.118.131101

We present a new scenario for generating the baryon asymmetry of the universe that is induced by a Nambu-Goldstone (NG) boson. The shift symmetry naturally controls the operators in the theory, while allowing the NG boson to couple to the spacetime geometry. The cosmological background thus sources a coherent motion of the NG boson, which leads to baryogenesis. Good candidates of the baryon-generating NG boson are the QCD axion and axion-like fields. In these cases the axion induces baryogenesis in the early universe, and can also serve as dark matter in the late universe.

So this paper takes modern axion cosmological model building and then runs with it.

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Early Cosmological Axion Production Models Reconsidered

by Tommy on 4/05/2017

There is still considerable resistance to the axion hypothesis in the string theory community.

Axions, Instantons, and the Lattice, Michael Dine, Patrick Draper, Laurel Stephenson-Haskins and Di Xu (1 May 2017)

If the QCD axion is a significant component of dark matter, and if the universe was once hotter than a few hundred MeV, the axion relic abundance depends on the function χ(T), the temperature-dependent topological susceptibility. Uncertainties in this quantity induce uncertainties in the axion mass as a function of the relic density, or vice versa. At high temperatures, theoretical uncertainties enter through the dilute instanton gas computation, while in the intermediate and strong coupling regime, only lattice QCD can determine χ(T) precisely. We reassess the uncertainty on the instanton contribution, arguing that it amounts to less than a factor of 20 in χ at T = 1.5 GeV. We then combine the instanton uncertainty with a range of models for χ(T) at intermediate temperatures and determine the impact on the axion relic density. We find that for a given relic density and initial misalignment angle, the combined uncertainty amounts to a factor of 2-3 in the zero-temperature axion mass.

I’ll be the first to admit there may be an axion mass distribution with a long low mass tail.

So they can flail around all they want with this.

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Cubic Reference Lattice of Bismuth Superconductivity Proposed

by Tommy on 4/05/2017

It looks like somebody already beat me to it.

Theory of Ultra Low Tc Superconductivity in Bismuth: Tip of an Iceberg?, G. Baskaran (3 May 2017)

Superconductivity with an ultra low Tc ∼ 0.5 mK was discovered recently in bismuth, a semimetal. To develop a model and scenario for Bi we begin with a cubic reference lattice, close to A7 (dimerized cubic) structure of Bi. Three valence electrons hop among 6px, 6py and 6pz orbitals and form quasi one dimensional chains at half filling}. An interesting interplay follows: i) Mott localization tendency in the chains, ii) metallization by interchain hopping and iii) lattice dimerization by electron-phonon coupling. In our proposal, a potential high Tc superconductivity from RVB mechanism is lost in the game. However some superconducting fluctuations survive. Tiny fermi pockets seen in Bi are viewed as remnant evanescent Bogoliubov quasi particles} in an anomalous normal state. Multi band character admits possibility of PT violating chiral singlet superconductivity}. Bi has a strong spin orbit coupling; Kramers theorem protects our proposal for the bulk by replacing real spin by Kramer pair. Control of chain dimerization might resurrect high Tc superconductivity in Bi, Sb and As.

This far better than I could have done, a serious paper with a unique approach.

The problem is reconciling cubic with the trigonal mess.

This is coming whether you like it or not.

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Topoelectric RLC Circuit Simulation of Topological Semimetals

by Tommy on 3/05/2017

Topolectrical circuits, Ching Hua Lee and Ronny Thomale (2 May 2017)

First developed by Alessandra Volta and Felix Savary in the early 19th century, circuits consisting of resistor, inductor and capacitor (RLC) components are now omnipresent in modern technology. The behavior of an RLC circuit is governed by its circuit Laplacian, which is analogous to the Hamiltonian describing the energetics of a physical system. We show that “topolectrical” boundary resonances (TBRs) appear in the impedance read-out of a circuit whenever its Laplacian bandstructure resembles that of topological semimetals – materials with extensive degenerate edge modes known as Fermi arcs that also harbor enigmatic transport properties. Such TBRs not only provide unambiguous and highly robust signals for the presence of a topological phase, but also promise diverse applicability within high density electronic mode processing. Due to the versatility of electronic circuits, our topological semimetal construction can be generalized to topolectrical phases with any desired lattice symmetry, spatial dimension, and even quasiperiodicity. Topolectrical circuits establish a bridge between electrical engineering and topological states of matter, where the accessibility, scalability, and operability of electronics promises to synergize with the intricate boundary properties of topological phases.

There is not much that I can add to this, it seems seminal if it works.

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Quasi 1D Gapped Topological Surface States in Bi on InSb

by Tommy on 1/05/2017

I’ve been trying desperately to get back to my first true science love – bismuth.

It wasn’t my first science. It was the first where I could openly claim some fame.

And after all these years I am still trying to figure it all out, even as the expert on it.

Spin-polarized quasi 1D state with finite bandgap on the Bi/InSb(001) surface, J. Kishi, Y. Ohtsubo, K. Yaji, A. Harasawa, F. Komori, S. Shin, J. E. Rault, P. Le Fèvre, F. Bertran, A. Taleb-Ibrahimi, M. Nurmamat, H. Yamane, S. Ideta, K. Tanaka and S. Kimura (18 April 2017)

One-dimensional (1D) electronic states were discovered on 1D surface atomic structure of Bi fabricated on semiconductor InSb(001) substrates by angle-resolved photoelectron spectroscopy (ARPES). The 1D state showed steep, Dirac-cone-like dispersion along the 1D atomic structure with a finite direct bandgap opening as large as 150 meV. Moreover, spin-resolved ARPES revealed the spin polarization of the 1D unoccupied states as well as that of the occupied states, the orientation of which inverted depending on the wave vector direction parallel to the 1D array on the surface. These results reveal that a spin-polarized quasi-1D carrier was realized on the surface of 1D Bi with highly efficient backscattering suppression, showing promise for use in future spintronic and energy-saving devices.

And after 30 years it’s long past the time that I write up what I know about this subject again.

A whole bunch of metal chalcogenides keep stealing my fire.

I suppose I had better get started on it.

Update: I’m almost anxious enough to start. That’s really the only way I can write.

To your horror you can watch it online. It might not end up looking anything like this though.

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I Wear the Crown of Science

by Tommy on 29/04/2017

It’s official. Science is king and I’m the boss.

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Cosmic Microwave Background CMB Cold Spot Controversy

by Tommy on 28/04/2017

Even with all the recent post deletions, I seem to be stuck on post number 666. That’s very bad.

Since I am definitely afflicted with a very mild case of small positive integer factoring numerology neurosis (AKA Number Theory), that is an unacceptable situation to be in for very long. People might start to talk. Rumors may arise as to my true motivations. Therefore I recently ran across this. I was vaguely aware there was a minor temperature anomaly hidden in there but I never really researched it. So when it showed up in the popular press along with the multiverse mania I decided to investigate it. And then of course I had a crackpot idea. And crackpot ideas are meant to be shared. You never know what might come out of that. Certainly not the Multiverse.

Evidence against a supervoid causing the CMB Cold Spot, Ruari Mackenzie, Tom Shanks, Malcolm N. Bremer, Yan-Chuan Cai, Madusha L.P. Gunawardhana, András Kovács, Peder Norberg and Istvan Szapudi, Submitted to MNRAS (12 April 2017)

We report the results of the 2dF-VST ATLAS Cold Spot galaxy redshift survey (2CSz) based on imaging from VST ATLAS and spectroscopy from 2dF AAOmega over the core of the CMB Cold Spot. We sparsely surveyed the inner 5 radius of the Cold Spot to a limit of iAB ≤ 19.2, sampling ∼ 7000 galaxies at z < 0.4. We have found voids at z = 0.14, 0.26 and 0.30 but they are interspersed with small over-densities and the scale of these voids is insufficient to explain the Cold Spot through the ΛCDM ISW effect. Combining with previous data out to z ∼ 1, we conclude that the CMB Cold Spot could not have been imprinted by a void confined to the inner core of the Cold Spot. Additionally we find that our 'control' field GAMA G23 shows a similarity in its galaxy redshift distribution to the Cold Spot. Since the GAMA G23 line-of-sight shows no evidence of a CMB temperature decrement we conclude that the Cold Spot may have a primordial origin rather than being due to line-of-sight effects.

See also: An Alternative View

Could multiple voids explain the Cosmic Microwave Background Cold Spot anomaly, Krishna Naidoo, Aurélien Benoit-Lévy and Ofer Lahav, Mon Not R Astron Soc Lett 459 (1): L71-L75. (20 March 2016), DOI:10.1093/mnrasl/slw043

Understanding the observed Cold Spot (CS) (temperature of ~ -150 μK at its center) on the Cosmic Microwave Background (CMB) is an outstanding problem. Explanations vary from assuming it is just a > 3 sigma primordial Gaussian fluctuation to the imprint of a supervoid via the Integrated Sachs-Wolfe and Rees-Sciama (ISW+RS) effects. Since single spherical supervoids cannot account for the full profile, the ISW+RS of multiple line-of-sight voids is studied here to mimic the structure of the cosmic web. Two structure configurations are considered. The first, through simulations of 20 voids, produces a central mean temperature of ~ -50 μK. In this model the central CS temperature lies at ~ 2 sigma but fails to explain the CS hot ring. An alternative multi-void model (using more pronounced compensated voids) produces much smaller temperature profiles, but contains a prominent hot ring. Arrangements containing closely placed voids at low redshift are found to be particularly well suited to produce CS-like profiles. We then measure the significance of the CS if CS-like profiles (which are fitted to the ISW+RS of multi-void scenarios) are removed. The CS tension with the LCDM model can be reduced dramatically for an array of temperature profiles smaller than the CS itself.

So what is my crackpot theory? Sorry, I already killed it off. It’s not the multiverse, though.

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Emergent Metastable Order Through Topological Excitation

by Tommy on 27/04/2017

Besides having a Synchrotron Radiation Center in my back yard, and a world class research university in my front yard, Dragan Mihailovic was probably my biggest influence when I first became seriously interested in the spectroscopy of high temperature superconductivity.

Long range electronic order in a metastable state created by ultrafast topological transformation, Yaroslav A. Gerasimenko, Igor Vaskivskyi and Dragan Mihailovic (26 April 2017)

The fundamental idea that many body systems in complex materials may self-organise into long range order under highly non-equilibrium conditions leads to the notion that entirely new emergent states with new and unexpected functionalities might be created. In this paper we show for the first time that a complex metastable state with long range order can be created through a non-equilibrium topological transformation in a transition metal dichalcogenide. Combining ultrafast optical pulse excitation with orbitally-resolved large-area scanning tunnelling microscopy we find subtle, but unambiguous evidence for long range electronic order which is different from all other known states in the system, and whose complex domain structure is not random, but is described by harmonics of the underlying charge density wave order. We show that the structure of the state is topologically distinct from the ground state, elucidating the origins of its remarkable metastability. These fundamental insights on the mechanism open the way to in-situ engineering of the emergent properties of metastable materials with ultrafast laser pulses.

What a long and winding road it’s been.

Pumping and probing.

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