Engineered Van der Waals Multilayer Heterojunction Excitons

by Tommy on 16/05/2016

http://arxiv.org/abs/1605.04057

Near-Unity Absorption in Van der Waals Semiconductors for Ultrathin Photovoltaics, Deep Jariwala, Artur R. Davoyan, Giulia Tagliabue, Michelle C. Sherrott, Joeson Wong and Harry A. Atwater (13 May 2016)

Key criteria for high efficiency photovoltaics include achieving high radiative efficiency, maximizing above-bandgap semiconductor absorption, and enabling carrier-selective charge collection at the cell operating point that exploits the full quasi-Fermi level separation for the carriers. High efficiency inorganic photovoltaic materials (e.g., Si, GaAs and GaInP) can achieve these criteria, but thin film photovoltaic absorbers have lacked the ability to fulfill one or more of these criteria, often due to surface and interface recombination effects. In contrast, Van der Waals semiconductors have naturally passivated surfaces with electronically active edges that allows retention of high electronic quality down-to the atomically thin limit and recent reports suggest that Van der Waals semiconductors can achieve the first criterion of high radiative efficiency. Here, we report that the second criteria for high efficiency of near-unity light absorption is possible in extremely thin (< 15 nm) Van der Waals semiconductor structures by coupling to strongly damped optical modes of semiconductor/metal heterostructures. We demonstrate near unity, broadband absorbing photovoltaic devices using sub-15 nm thick transition metal dichalcogenides (TMDCs) as van der Waals semiconductor active layers. Our TMDC devices show a short circuit current density > 10 mA/cm2 at ~ 20 Suns and exhibits spectral response that parallels the spectral absorption over the above bandgap region. Our work addresses one of the key criteria to enable TMDCs to achieve high photovoltaic efficiency.

See also: http://arxiv.org/abs/1605.04255

Engineering and Manipulating Structured Excitons, Xiaoning Zang, Simone Montangero, Lincoln D. Carr and Mark T. Lusk (13 May 2016)

When a semiconductor absorbs light, the resulting electron-hole superposition amounts to a uncontrolled quantum ripple that eventually degenerates into diffusion (Frenkel 1931, Wannier 1937, Lanzani 2012). If the conformation of these excitonic superpositions could be engineered, though, they would constitute a new means of transporting information and energy. We show that properly designed laser pulses can be used to create such structured excitons. They can be formed with a prescribed speed, direction and spectral make-up that allows them to be selectively passed, rejected or even dissociated using superlattices. Their coherence also provides a handle for manipulation using active, external controls. Energy and information can be conveniently processed and subsequently removed at a distant site by reversing the original procedure to produce a stimulated emission. The ability to create, manage and remove structured excitons comprises the foundation for opto-excitonic circuits with application to a wide range of quantum information, energy and light-flow technologies. The paradigm is demonstrated using both tight-binding and Time-Domain Density Functional Theory simulations.

I don’t quite understand what the hold up with this could be.

Commercial capital, or government funding?

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Superconductors as (Very) Light Axion Dark Matter Absorbers

by Tommy on 16/05/2016

http://arxiv.org/abs/1604.06800

Detecting Ultralight Bosonic Dark Matter via Absorption in Superconductors, Yonit Hochberg, Tongyan Lin and Kathryn M. Zurek (22 April 2016)

Superconducting targets have recently been proposed for the direct detection of dark matter as light as a keV, via elastic scattering off conduction electrons in Cooper pairs. Detecting such light dark matter requires sensitivity to energies as small as the superconducting gap of O(meV). Here we show that these same superconducting devices can detect much lighter DM, of meV to eV mass, via dark matter absorption on a conduction electron, followed by emission of an athermal phonon. We demonstrate the power of this setup for relic kinetically mixed hidden photons, pseudoscalars, and scalars, showing the reach can exceed current astrophysical and terrestrial constraints with only a moderate exposure.

See also: http://arxiv.org/abs/1504.07237

Superconducting Detectors for Super Light Dark Matter, Yonit Hochberg, Yue Zhao and Kathryn M. Zurek, Phys. Rev. Lett. 116, 011301 (7 January 2016), doi:10.1103/PhysRevLett.116.011301

We propose and study a new class of superconducting detectors which are sensitive to O(meV) electron recoils from dark matter-electron scattering. Such devices could detect dark matter as light as the warm dark matter limit, mX > keV. We compute the rate of dark matter scattering off of free electrons in a (superconducting) metal, including the relevant Pauli blocking factors. We demonstrate that classes of dark matter consistent with terrestrial and cosmological/astrophysical constraints could be detected by such detectors with a moderate size exposure.

With topological superconductors I can detect fluctuating dynamical axion fields as well.

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Sulfur Isotopes Date Great Atmospheric Oxygen Inversion Event

by Tommy on 14/05/2016

http://advances.sciencemag.org/content/2/5/e1600134

Rapid oxygenation of Earth’s atmosphere 2.33 billion years ago, Genming Luo, Shuhei Ono, Nicolas J. Beukes, David T. Wang, Shucheng Xie and Roger E. Summons, Science Advances 2, 5, e1600134 (6 May 2016), doi:10.1126/sciadv.1600134

Molecular oxygen (O2) is, and has been, a primary driver of biological evolution and shapes the contemporary landscape of Earth’s biogeochemical cycles. Although “whiffs” of oxygen have been documented in the Archean atmosphere, substantial O2 did not accumulate irreversibly until the Early Paleoproterozoic, during what has been termed the Great Oxygenation Event (GOE). The timing of the GOE and the rate at which this oxygenation took place have been poorly constrained until now. We report the transition (that is, from being mass-independent to becoming mass-dependent) in multiple sulfur isotope signals of diagenetic pyrite in a continuous sedimentary sequence in three coeval drill cores in the Transvaal Supergroup, South Africa. These data precisely constrain the GOE to 2.33 billion years ago. The new data suggest that the oxygenation occurred rapidly—within 1 to 10 million years—and was followed by a slower rise in the ocean sulfate inventory. Our data indicate that a climate perturbation predated the GOE, whereas the relationships among GOE, “Snowball Earth” glaciation, and biogeochemical cycling will require further stratigraphic correlation supported with precise chronologies and paleolatitude reconstructions.

It’s quite possible the oxygen was there all along in the upper atmosphere and the climate perturbation initiated a great atmospheric oxygen inversion layer collapse to the surface, resulting in geologically instantaneous oxygenation. That’s my crackpot theory at this point.

This will take a while to sort out.

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Early Earth Achaean Atmosphere Was Chemically Differentiated

by Tommy on 12/05/2016

http://www.nature.com/nature/journal/v533/n7602/full/nature17678.html

Ancient micrometeorites suggestive of an oxygen-rich Archaean upper atmosphere, Andrew G. Tomkins, Lara Bowlt, Matthew Genge, Siobhan A. Wilson, Helen E. A. Brand and Jeremy L. Wykes, Nature, 533, 235–238 (11 May 2016), doi:10.1038/nature17678

It is widely accepted that Earth’s early atmosphere contained less than 0.001 per cent of the present-day atmospheric oxygen (O2) level, until the Great Oxidation Event resulted in a major rise in O2 concentration about 2.4 billion years ago. There are multiple lines of evidence for low O2 concentrations on early Earth, but all previous observations relate to the composition of the lower atmosphere in the Archaean era; to date no method has been developed to sample the Archaean upper atmosphere. We have extracted fossil micrometeorites from limestone sedimentary rock that had accumulated slowly 2.7 billion years ago before being preserved in Australia’s Pilbara region. We propose that these micrometeorites formed when sand-sized particles entered Earth’s atmosphere and melted at altitudes of about 75 to 90 kilometres (given an atmospheric density similar to that of today). Here we show that the FeNi metal in the resulting cosmic spherules was oxidized while molten, and quench-crystallized to form spheres of interlocking dendritic crystals primarily of magnetite (Fe3O4), with wüstite (FeO)+metal preserved in a few particles. Our model of atmospheric micrometeorite oxidation suggests that Archaean upper-atmosphere oxygen concentrations may have been close to those of the present-day Earth, and that the ratio of oxygen to carbon monoxide was sufficiently high to prevent noticeable inhibition of oxidation by carbon monoxide. The anomalous sulfur isotope (Δ33S) signature of pyrite (FeS2) in seafloor sediments from this period, which requires an anoxic surface environment, implies that there may have been minimal mixing between the upper and lower atmosphere during the Archaean.

I suppose this would be the greenhouse gas and oxygen companion to the previous article.

They told me when I was a young child that I would not start to know the answers to some of these questions before the second decade of the next century, and I now remember how disappointed I was that there would be no flat screen TVs and Dick Tracy watches any time soon, but here it is already now, the 2nd decade of the 21st century, and they were right!

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This is Your Only Planet Earth on Carbon Dioxide Steroids

by Tommy on 12/05/2016
Planet Earth Average Global Surface Temperature Anomaly

Planet Earth Average Global Surface Temperature Anomaly

Fort McMurray citizens can now get back to their important task of profiting from destruction.

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Monolayer Arsenene and Antimonene Allotropes Studied

by Tommy on 10/05/2016

http://arxiv.org/abs/1604.03422

First-principle calculations of phononic, electronic and optical properties of monolayer arsenene and antimonene allotropes, Yuanfeng Xu, Bo Peng, Hao Zhang, Hezhu Shao, Rongjun Zhang, Hongliang Lu, David Wei Zhang and Heyuan Zhu (12 April 2016)

Recently a stable monolayer of antimony in buckled honeycomb structure called antimonene was successfully grown on 3D topological insulator Bi2Te3 and Sb2Te3, which displays semiconducting properties. By first principle calculations, we systematically investigate the phononic, electronic and optical properties of α− and β− allotropes of monolayer arsenene/antimonene. We investigate the dynamical stabilities of these four materials by considering the phonon dispersions. The obtained electronic structures reveal the direct band gap of monolayer α−As/Sb and indirect band gap of β−As/Sb. Significant absorption is observed in α−Sb, which can be used as a broad saturable absorber.

See also: http://pubs.acs.org/doi/abs/10.1021/acsami.5b02441

Atomically Thin Group V Elemental Films: Theoretical Investigations of Antimonene Allotropes, Gaoxue Wang, Ravindra Pandey and Shashi P. Karna, ACS Appl. Mater. Interfaces, 2015, 7 (21), pp 11490–11496 (8 May, 2015), DOI:10.1021/acsami.5b02441

Group V elemental monolayers including phosphorene are emerging as promising 2D materials with semiconducting electronic properties. Here, we present the results of first-principles calculations on stability, mechanical and electronic properties of 2D antimony (Sb), antimonene. Our calculations show that free-standing α and β allotropes of antimonene are stable and semiconducting. The α-Sb has a puckered structure with two atomic sublayers and β-Sb has a buckled hexagonal lattice. The calculated Raman spectra and STM images have distinct features thus facilitating characterization of both allotropes. The β-Sb has nearly isotropic mechanical properties, whereas α-Sb shows strongly anisotropic characteristics. An indirect–direct band gap transition is expected with moderate tensile strains applied to the monolayers, which opens up the possibility of their applications in optoelectronics.

I’m not quite sure if I covered this earlier or not.

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Early Archaean Earth Atmosphere Less Than Half of Today’s

by Tommy on 10/05/2016

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2713.html

Earth’s air pressure 2.7 billion years ago constrained to less than half of modern levels, Sanjoy M. Som, Roger Buick, James W. Hagadorn, Tim S. Blake, John M. Perreault, Jelte P. Harnmeijer and David C. Catling, Nature Geoscience (9 May 2016), doi:10.1038/ngeo2713

How the Earth stayed warm several billion years ago when the Sun was considerably fainter is the long-standing problem of the ‘faint young Sun paradox’. Because of negligible O2 and only moderate CO2 levels in the Archaean atmosphere, methane has been invoked as an auxiliary greenhouse gas. Alternatively, pressure broadening in a thicker atmosphere with a N2 partial pressure around 1.6–2.4 bar could have enhanced the greenhouse effect. But fossilized raindrop imprints indicate that air pressure 2.7 billion years ago (Gyr) was below twice modern levels and probably below 1.1 bar, precluding such pressure enhancement. This result is supported by nitrogen and argon isotope studies of fluid inclusions in 3.0 – 3.5 Gyr rocks. Here, we calculate absolute Archaean barometric pressure using the size distribution of gas bubbles in basaltic lava flows that solidified at sea level ~ 2.7 Gyr in the Pilbara Craton, Australia. Our data indicate a surprisingly low surface atmospheric pressure of Patm = 0.23 ± 0.23 (2σ) bar, and combined with previous studies suggests ~ 0.5 bar as an upper limit to late Archaean Patm. The result implies that the thin atmosphere was rich in auxiliary greenhouse gases and that Patm fluctuated over geologic time to a previously unrecognized extent.

The origin and evolution of the nitrogen component of Earth’s atmosphere has been high on my unsolved problemS list since I was a very young child. It’s nice to finally see even subtle hints of some of the answers here. The same goes for Mars. It starts with big early planetoid impacts.

Update: And big close planetoid flybys too, apparently.

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Atomic Quantum Simulation of 3D U(1) Gauge Higgs Model

by Tommy on 10/05/2016

http://arxiv.org/abs/1605.02502

Atomic quantum simulation of a three-dimensional U(1) gauge-Higgs model, Yoshihito Kuno, Shinya Sakane, Kenichi Kasamatsu, Ikuo Ichinose and Tetsuo Matsui (9 May 2016)

In this paper, we study atomic quantum simulations of a U(1) gauge-Higgs model on a three-dimensional (3D) spatial lattice. We start from an extended 3D Bose-Hubbard model with nearest-neighbor repulsions and show that it can simulate a U(1) gauge-Higgs model with next nearest-neighbor Higgs couplings. Here the phase of the boson variable on each site of the optical lattice describes the vector potential on each link of the gauge-model lattice. To determine the phase diagram of the gauge-Higgs model at a zero temperature, we perform Monte-Carlo simulations of the corresponding 3+1-dimensional U(1) gauge-Higgs model, and obtain the three phases, i.e., the confinement, Coulomb and Higgs phases. To investigate the dynamical properties of the gauge-Higgs model, we apply the Gross-Pitaevskii equations to the extended Bose-Hubbard model. We simulate the time-evolution of an electric flux initially put on a straight line connecting two external point charges. We also calculate the potential energy between this pair of charges and obtain the string tension in the confinement phase. Finally, we propose a feasible experimental setup for the atomic simulations of this quantum gauge-Higgs model in the 3D optical lattice.

This is going straight into my autobiogenesis essay.

http://lifeform.net/archimedes/Cosmic_Evolution.pdf

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Binary Group V – V Monolayer Bonding Compounds Sought

by Tommy on 10/05/2016

https://arxiv.org/abs/1510.04108

Atomically thin binary V-V compound semiconductor: a first-principles study, Weiyang Yu, Zhili Zhu, Chun-Yao Niu, Xiaolin Cai and Wei-Bing Zhang (6 April 2016)

Searching the novel 2D semiconductor is crucial to develop the next-generation low-dimensional electronic device. Using first-principles calculations, we propose a class of unexplored binary V-V compound semiconductor (PN, AsN, SbN, AsP, SbP and SbAs) with monolayer black phosphorene (α) and blue phosphorene (β) structure. Our phonon spectra and room-temperature molecular dynamics (MD) calculations indicate that all compounds are very stable. Moreover, most of compounds are found to present a moderate energy gap in the visible frequency range, which can be tuned gradually by in-plane strain. Especially, α-phase V-V compounds have a direct gap while β-SbN, AsN, SbP, and SbAs may be promising candidates of 2D solar cell materials due to a wide gap separating acoustic and optical phonon modes. Furthermore, vertical heterostructures can be also built using lattice matched α(β)-SbN and phosphorene, and both vdW heterostructures are found to have intriguing direct band gap. The present investigation not only broads the scope of layered group V semiconductors but also provides an unprecedented route for the potential applications of 2D V-V families in optoelectronic and nanoelectronic semiconductor devices.

Moving onwards inexorably, as if drawn by a magnet.

Or as Mothra to Godzilla.

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Fort McMurray, Alberta, Northern Canada is Feeling the Bern

by Tommy on 7/05/2016
Fort McMurray Convoy Wildfire Evacuation

Fort McMurray Convoy Wildfire Evacuation

I have no sympathy for these idiots. I will not shed a tear or contribute one cent for their welfare.

They richly deserve the punishment that nature is giving them.

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Dirac Monopoles from Weyl Hamiltonian by Green’s Functions

by Tommy on 4/05/2016

http://arxiv.org/abs/1605.00759

Topological Numbers and the Weyl Semimetal, Mahmut Elbistan (3 May 2016)

Generalized Dirac monopoles in momentum space are constructed in even d+1 dimensions from the Weyl Hamiltonian in terms of Green’s functions. In 3+1 spacetime dimensions, the (unit) charge of the monopole is equal to both the winding number and the Chern number, expressed as the integral of the Berry curvature. Based on the equivalence of the Chern and winding numbers, a chirally coupled field theory action is proposed for the Weyl semimetal phase. At the one loop order, the effective action yields both the chiral magnetic effect and the anomalous Hall effect. The Chern number appears as a coefficient in the conductivity, thus emphasizes the role of topology. The anomalous contribution of chiral fermions to transport phenomena is reflected as the gauge anomaly with the topological term E . B. Relevance of monopoles and Chern numbers for the semiclassical chiral kinetic theory is also discussed.

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Kibble – Zurek Mechanism Simulated in Cold Atom Systems

by Tommy on 4/05/2016

http://arxiv.org/abs/1605.01023

Universal space-time scaling symmetry in the dynamics of bosons across a quantum phase transition, Logan W. Clark, Lei Feng and Cheng Chin (3 May 2016)

The dynamics of many-body systems spanning condensed matter, cosmology, and beyond is hypothesized to be universal when the systems cross continuous phase transitions. The universal dynamics is expected to satisfy a scaling symmetry of space and time with the crossing rate, inspired by the Kibble-Zurek mechanism. We test this symmetry based on Bose condensates in a shaken optical lattice. Shaking the lattice drives condensates across an effectively ferromagnetic quantum phase transition. After crossing the critical point, the condensates manifest delayed growth of spin fluctuations and develop anti-ferromagnetic spatial correlations resulting from sub-Poisson generation of topological defects. The characteristic times and lengths scale as power-laws of the crossing rate, yielding the temporal exponent 0.50(2) and the spatial exponent 0.26(2), consistent with theory. Furthermore, the fluctuations and correlations are invariant in scaled space-time coordinates, in support of the scaling symmetry of quantum critical dynamics.

To Infinity, And Beyond!

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I, Tommy – I’m Naming the SI Unit of Momentum After Myself

by Tommy on 30/04/2016
Higgs Particle Collision

Higgs Particle Collision

Ok, after inventing the scientific domain of engineering science, and then going on to invent the subdomain of ‘quantum astrophysics’, what do I do for an encore? Well, I did this quite a while ago during the era of the static ISP website, simple javascripts and AJAX, on my fundamental physical and chemical units, symbols and constants pages and then in my infamous AJAXified interactive periodic table of the elements. The SI unit of momentum is mine! I’m claiming it. Me.

SI Unit of Momentum

Symbol : I (Impulse)

Name : Fritz

Units : kg m s-1

You heard it here first. I can’t remember if I ever posted this to the usenet.

I dare you to out crackpot this.

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Growth, Transport Properties – Bismuth on Potassium Chloride

by Tommy on 29/04/2016

http://scitation.aip.org/content/aip/journal/jap/119/13/10.1063/1.4945036

Semiconductor- to metallic-like behavior in Bi thin films on KCl substrate, Thanh Nhan Bui, Jean-Pierre Raskin and Benoit Hackens, J. Appl. Phys. 119, 135304 (5 April 2016); DOI:10.1063/1.4945036

Bi thin films, with a thickness of 100 nm, are deposited by electron-beam evaporation on a freshly cleaved (100) KCl substrate. The substrate temperature during film growth (Tdep) ranges from room temperature up to 170 °C. Films deposited at room temperature exhibit a maze-like microstructure typical of the rhombohedral (110) texture, as confirmed by X-ray diffraction. For Tdep above 80 °C, a different microstructure appears, characterized by concentric triangular shapes corresponding to the trigonal (111) texture. Temperature dependence of the resistivity shows a transition from a semiconductor-like behavior for films deposited at room temperature to a metallic-like behavior for Tdep above 80 °C. From magnetoresistance measurements between room temperature and 1.6 K, we extract the electron and hole mobilities, concentrations, and mean free paths, which allow to draw a complete picture of the transport properties of both types of films.

Ok, back to the grind.

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CDW Phase Diagram of the Cuprates Further Refined Yet Again

by Tommy on 28/04/2016
Dynamic Fluctuating CDW Cuprate Phase Diagram

Dynamic Fluctuating CDW Cuprate Phase Diagram

http://arxiv.org/abs/1604.07852

Dynamical charge density waves rule the phase diagram of cuprates, S. Caprara, C. Di Castro, G. Seibold and M. Grilli (26 April 2016)

In the last few years charge density waves (CDWs) have been ubiquitously observed in cuprates and are now the most investigated among the competing orders in the longstanding (but still hot) debate on high-temperature superconducting cuprates. Different dome-shaped CDW onset lines in the temperature vs. doping phase diagram are detected by experiments with probes having different characteristic timescales. These lines are extrapolated at zero temperature to different quantum critical points (QCPs) in agreement with the long-standing theoretical result that CDW’s are present in these systems and disappear with a QCP by increasing doping. This QCP is buried underneath the superconducting dome, in the optimal doping region (i.e., where the superconducting critical temperature Tc is highest). A wealth of new experimental data raise fundamental issues that challenge the various theoretical proposals. Here, we reproduce the complex experimental phase diagram and provide a coherent solution to all these problems based on the occurrence of dynamically fluctuating CDWs.

Who did not see this coming?

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Optimum Performance of Thermoelectric Energy Conversion

by Tommy on 28/04/2016

http://arxiv.org/abs/1604.07551

Thermoelectric energy converters under a trade-off figure of merit with broken time-reversal symmetry, I. Iyyappan and M. Ponmurugan (26 April 2016)

We study the optimum performance of the thermoelectric energy converters such as heat engines and refrigerators with broken time-reversal symmetry by applying unified trade-off figure of merit Ω˙, which takes the account of best compromise between the maximum work extraction and the minimum work loss. We find that the maximum Ω˙ criterion provide the significantly high performance of the thermoelectric energy converter if the system possess reasonably large value of the asymmetric parameter as compared to the maximum χ criterion. However, the maximum χ criterion provide the better performance than the maximum Ω˙ criterion for low value of the asymmetric parameter. Our results can be useful to design high efficient real thermoelectric heat engines and refrigerators with broken time-reversal symmetry.

These kinds of in depth analyses are extremely insightful and helpful.

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Quantum Proton Tunneling of Water Molecules Trapped in Beryl

by Tommy on 26/04/2016

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.167802

Quantum Tunneling of Water in Beryl: A New State of the Water Molecule, Alexander I. Kolesnikov, George F. Reiter, Narayani Choudhury, Timothy R. Prisk, Eugene Mamontov, Andrey Podlesnyak, George Ehlers, Andrew G. Seel, David J. Wesolowski and Lawrence M. Anovitz, Phys. Rev. Lett., 116, 167802 (22 April 2016), DOI:10.1103/PhysRevLett.116.167802

Using neutron scattering and ab initio simulations, we document the discovery of a new “quantum tunneling state” of the water molecule confined in 5 Å channels in the mineral beryl, characterized by extended proton and electron delocalization. We observed a number of peaks in the inelastic neutron scattering spectra that were uniquely assigned to water quantum tunneling. In addition, the water proton momentum distribution was measured with deep inelastic neutron scattering, which directly revealed coherent delocalization of the protons in the ground state.

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Boron 11B Nuclear Isotopes Constrain CO2 Climate Forcing

by Tommy on 26/04/2016

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature17423.html

Changing atmospheric CO2 concentration was the primary driver of early Cenozoic climate, Eleni Anagnostou, Eleanor H. John, Kirsty M. Edgar, Gavin L. Foster, Andy Ridgwell, Gordon N. Inglis, Richard D. Pancost, Daniel J. Lunt and Paul N. Pearson, Nature (25 April 2016), doi:10.1038/nature17423

The Early Eocene Climate Optimum (EECO, which occurred about 51 to 53 million years ago), was the warmest interval of the past 65 million years, with mean annual surface air temperature over ten degrees Celsius warmer than during the pre-industrial period. Subsequent global cooling in the middle and late Eocene epoch, especially at high latitudes, eventually led to continental ice sheet development in Antarctica in the early Oligocene epoch (about 33.6 million years ago). However, existing estimates place atmospheric carbon dioxide (CO2) levels during the Eocene at 500 – 3,000 parts per million, and in the absence of tighter constraints carbon–climate interactions over this interval remain uncertain. Here we use recent analytical and methodological developments to generate a new high-fidelity record of CO2 concentrations using the boron isotope (δ11B) composition of well preserved planktonic foraminifera from the Tanzania Drilling Project, revising previous estimates. Although species-level uncertainties make absolute values difficult to constrain, CO2 concentrations during the EECO were around 1,400 parts per million. The relative decline in CO2 concentration through the Eocene is more robustly constrained at about fifty percent, with a further decline into the Oligocene. Provided the latitudinal dependency of sea surface temperature change for a given climate forcing in the Eocene was similar to that of the late Quaternary period, this CO2 decline was sufficient to drive the well documented high- and low-latitude cooling that occurred through the Eocene. Once the change in global temperature between the pre-industrial period and the Eocene caused by the action of all known slow feedbacks (apart from those associated with the carbon cycle) is removed, both the EECO and the late Eocene exhibit an equilibrium climate sensitivity relative to the pre-industrial period of 2.1 to 4.6 degrees Celsius per CO2 doubling (66 percent confidence), which is similar to the canonical range (1.5 to 4.5 degrees Celsius), indicating that a large fraction of the warmth of the early Eocene greenhouse was driven by increased CO2 concentrations, and that climate sensitivity was relatively constant throughout this period.

Now you know you be fucked. It’s official. I’m just not seeing those electric cars on the road.

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Future Higgs Portal into Electroweak Cosmology Discussed

by Tommy on 22/04/2016

http://arxiv.org/abs/1604.05324

The Higgs Portal and Cosmology, Ketevi Assamagan, Chien-Yi Chen, John Paul Chou, David Curtin, Michael A. Fedderke, Yuri Gershtein, Xiao-Gang He, Markus Klute, Jonathan Kozaczuk, Ashutosh Kotwal, Steven Lowette, Jose Miguel No, Tilman Plehn, Jianming Qian, Michael Ramsey-Musolf, Alexei Safonov, Jessie Shelton, Michael Spannowsky, Shufang Su, Devin G. E. Walker, Stephane Willocq and Peter Winslow, Summarization of the landscape of possibilities surveyed at the “Unlocking the Higgs Portal” Workshop held at the Amherst Center for Fundamental Interactions (ACFI) in May 2014, Report number ACFI-T16-10 (18 April 2016)

Higgs portal interactions provide a simple mechanism for addressing two open problems in cosmology: dark matter and the baryon asymmetry. In the latter instance, Higgs portal interactions may contain the ingredients for a strong first order electroweak phase transition as well as new CP-violating interactions as needed for electroweak baryogenesis. These interactions may also allow for a viable dark matter candidate. We survey the opportunities for probing the Higgs portal as it relates to these questions in cosmology at the LHC and possible future colliders.

More flailing around in the dark for the dark sector.

You gotta start somewhere.

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Some Ultralight Axion Like Particles Excluded by Observation

by Tommy on 22/04/2016

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.161101

Search for Spectral Irregularities due to Photon–Axionlike-Particle Oscillations with the Fermi Large Area Telescope, M. Ajello et al. (The Fermi-LAT Collaboration), Phys. Rev. Lett., 116, 161101 (20 April 2016), DOI:10.1103/PhysRevLett.116.161101

We report on the search for spectral irregularities induced by oscillations between photons and axionlike-particles (ALPs) in the γ-ray spectrum of NGC 1275, the central galaxy of the Perseus cluster. Using 6 years of Fermi Large Area Telescope data, we find no evidence for ALPs and exclude couplings above 5 × 10−12 GeV−1 for ALP masses 0.5 ≲ ma ≲ 5 neV at 95% confidence. The limits are competitive with the sensitivity of planned laboratory experiments, and, together with other bounds, strongly constrain the possibility that ALPs can reduce the γ-ray opacity of the Universe,

I haven’t read this paper, but this is a really poorly written abstract. We don’t know what ALPs are, we really don’t even know exactly what an axion is yet, and lattice QCD calculations already points to moderately heavy axions (not WIMP scale, ~ meV ~ keV ~), if they even exist at all.

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Happy Earth Day!

by Tommy on 22/04/2016
Lunar Reconnaissance Orbiter LRO Earth Moon Earthrise

Lunar Reconnaissance Orbiter LRO Earth Moon Earthrise

SpaceX – Launch and Land and Relaunch.

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Classical and Quantum Thermodynamic Heat Engines Probed

by Tommy on 17/04/2016

http://arxiv.org/abs/1604.03411

Periodic Thermodynamics of Open Quantum Systems, Kay Brandner and Udo Seifert (12 April 2016)

The thermodynamics of quantum systems coupled to periodically modulated heat baths and work reservoirs is developed. By identifying affinities and fluxes, the first and second law are formulated consistently. In the linear response regime, entropy production becomes a quadratic form in the affinities. Specializing to Lindblad-dynamics, we identify the corresponding kinetic coefficients in terms of correlation functions of the unperturbed dynamics. Reciprocity relations follow from symmetries with respect to time reversal. The kinetic coefficients can be split into a classical and a quantum contribution subject to a new constraint, which follows from a natural detailed balance condition. This constraint implies universal bounds on efficiency and power of quantum heat engines. In particular, we show that Carnot efficiency can not be reached whenever quantum coherence effects are present, i.e., when the Hamiltonian used for work extraction does not commute with the bare system Hamiltonian. For illustration, we specialize our universal results to a driven two-level system in contact with a heat bath of sinusoidally modulated temperature.

Udo Seifert continues to blaze a path with this. Here the result is that the most efficient coherent quantum energy up and down converters can do no useful work, and it appears that useful work extraction at maximum Carnot efficiency will also require an incoherent Fermi liquid and/or gas.

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Quantum Dualities Found in Arbitrarily Large Chern Numbers

by Tommy on 16/04/2016

http://arxiv.org/abs/1603.08517

Quantum Dualities and Quantum Anomalous Hall Phases with Arbitrary Large Chern Numbers, Tong Chern (28 March 2016)

Quantum duality is a far reaching concept in contemporary theoretical physics. In the present paper, we reveal the quantum dualities in quantum anomalous Hall (QAH) phases through concrete two bands Hamiltonian models. Our models can realize QAH phases with arbitrary large Chern numbers. In real materials these models may be realized by stacked n layer systems of c1 = 1 QAH insulators. The topological phase transitions that can change the Chern numbers are studied. And we investigate the gapless edge modes of our models in details, and find a new mechanism for the bulk boundary correspondence.

Again, this is so new and interesting all I can do is repeat it verbatim here.

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Engineering of Holographic Superconductivity Proposed

by Tommy on 16/04/2016

http://arxiv.org/abs/1603.08259

Engineering Holographic Superconductor Phase Diagrams, Jiunn-Wei Chen, Shou-Huang Dai, Debaprasad Maity and Yun-Long Zhang, Report Number MIT-CTP/4971 (27 March 2016)

We study how to engineer holographic models with features of a high temperature superconductor phase diagram. We introduce a field in the bulk which provides a tunable “doping” parameter in the boundary theory. By designing how this field changes the effective masses of other order parameter fields, desired phase diagrams can be engineered. We give examples of generating phase diagrams with phase boundaries similar to a superconducting dome and an anti-ferromagnetic phase by including two order parameter fields. We also explore whether the pseudo gap phase can be described without adding another order parameter field and discuss the potential scaling symmetry associated with a quantum critical point hidden under the superconducting dome in this phase diagram.

This is so interesting and timely that all I can do is urge you to slug your way through it.

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Hortonheardawho of Mars Rover Blog Image Processing Dies

by Tommy on 9/04/2016
Hortonheardawho Mars Surface Image

Hortonheardawho Mars Surface Image

https://www.flickr.com/photos/hortonheardawho/

I just heard that hortonheardawho passed away on February 25, 2016. Hort was a scientific and engineering genius who was the undisputed leader in Mars Rover image processing, posting his spectacular images on Mark Carey’s Mars Rover Blog. Mars Rover Blog forum software has always been super cranky, something left over from the CGI forum software days, and lately it’s starting to be hacked, but in its day it was the place to be for wild new hypotheses and crackpot ideas about Mars geology and the possibility of life on Mars. Hort was known for his identification and naming of the self ordering phenomena in the decaying soils of Mars – Hallucigenia and Psychedelia – aka SODs or Self Organizing Dust. His loss is great. But his work lives on.

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SpaceX Falcon 9 Booster Lands on a Drone Ship Barge

by Tommy on 8/04/2016
SpaceX Falcon 9 Booster Drone Ship

SpaceX Falcon 9 Booster Drone Ship

I feel another song coming on!

Let My People Go!

Update: April 12, 2016 – The ships are in port and the American Space Revolution has begun.

One if by land, two if by sea.

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Neutron Spectroscopy Reveals Hydrogen Rich Poles at Ceres

by Tommy on 7/04/2016
Ceres Dawn Hydrogen Distribution Neutron Spectroscopy

Ceres Dawn Hydrogen Distribution Neutron Spectroscopy

Ok then, forget Occator and the equator.

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Kaluza Geometry Favored by CERN LHC 750 GeV Resonance

by Tommy on 2/04/2016

http://www.hindawi.com/journals/jgrav/2015/901870/

Field Equations and Lagrangian for the Kaluza Metric Evaluated with Tensor Algebra Software, L. L. Williams, Journal of Gravity, 901870 (2015), DOI:10.1155/2015/901870

This paper calculates the Kaluza field equations with the aid of a computer package for tensor algebra, xAct. The xAct file is provided with this paper. We find that Thiry’s field equations are correct, but only under limited circumstances. The full five-dimensional field equations under the cylinder condition are provided here, and we see that most of the other references miss at least some terms from them. We go on to establish the remarkable Kaluza Lagrangian, and verify that the field equations calculated from it match those calculated with xAct, thereby demonstrating self-consistency of these results. Many of these results can be found scattered throughout the literature, and we provide some pointers for historical purposes. But our intent is to provide a definitive exposition of the field equations of the classical, five-dimensional metric ansatz of Kaluza, along with the computer algebra data file to verify them, and then to recover the unique Lagrangian for the theory. In common terms, the Kaluza theory is an “ω = 0″ scalar field theory, but with unique electrodynamic couplings.

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Dynamical Running Vacuum Models Favored Over Rigid ΛCDM

by Tommy on 2/04/2016

http://arxiv.org/abs/1602.02103

First evidence of running cosmic vacuum: challenging the concordance model, Joan Sola, Adria Gomez-Valent and Javier de Cruz Perez (5 February 2016)

Despite the fact that a rigid Λ-term is a fundamental building block of the concordance ΛCDM model, we show that a large class of cosmological scenarios with dynamical vacuum energy density ρΛ and/or gravitational coupling G, together with a possible non-conservation of matter, are capable of seriously challenging the traditional phenomenological success of the Λ-CDM. In this Letter, we discuss these “running vacuum models” (RVM’s), in which ρΛ=ρΛ(H) consists of a nonvanishing constant term and a series of powers of the Hubble rate. Such generic structure is potentially linked to the quantum field theoretical description of the expanding Universe. By performing an overall fit to the cosmological observables SNIα+BAO+H(z)+LSS+BBN+CMB (in which the WMAP9, Planck 2013 and Planck 2015 data are taken into account), we find that the RVM’s appear definitely more favored than the ΛCDM, namely at an unprecedented level of ∼4σ, implying that the ΛCDM is excluded at ∼99.99% c.l. Furthermore, the Akaike and Bayesian information criteria confirm that the dynamical RVM’s are strongly preferred as compared to the conventional rigid Λ-picture of the cosmic evolution.

This will be great for my report!

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The Image From Dawn At Ceres You’ve All Been Waiting For

by Tommy on 23/03/2016

Dawn_Ceres_Occator_Crater_Bright_Spot_Fractured_Dome_Salt_Mound

Occator Crater panorama from low mapping orbit.

Enjoy!

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Planet Ceres Sublimating Away Slowly – From Crust To Dust

by Tommy on 19/03/2016

http://arxiv.org/abs/1602.03467

http://mnrasl.oxfordjournals.org/content/458/1/L54

http://www.eso.org/public/archives/releases/sciencepapers/eso1609/eso1609a.pdf

Daily variability of Ceres’ Albedo detected by means of radial velocities changes of the reflected sunlight, P. Molaro, A. F. Lanza, L. Monaco, F. Tosi, G. Lo Curto, M. Fulle and L. Pasquini, Monthy Notices of the Royal Astronomical Society Letters (7 February 2016), DOI:10.1093/mnrasl/slw017

Bright features have been recently discovered by Dawn on Ceres, which extend previous photometric and Space Telescope observations. These features should produce distortions of the line profiles of the reflected solar spectrum and therefore an apparent radial velocity variation modulated by the rotation of the dwarf planet. Here we report on two sequences of observations of Ceres performed in the nights of 31 July, 26-27 August 2015 by means of the high-precision HARPS spectrograph at the 3.6-m La Silla ESO telescope. The observations revealed a quite complex behaviour which likely combines a radial velocity modulation due to the rotation with an amplitude of approx +/- 6 m/s and an unexpected diurnal effect. The latter changes imply changes in the albedo of Occator’s bright features due to the blaze produced by the exposure to solar radiation. The short-term variability of Ceres’ albedo is on timescales ranging from hours to months and can both be confirmed and followed by means of dedicated radial velocity observations.

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Dana Rohrabacher Introduces NASA Space Settlement Act

by Tommy on 18/03/2016

https://www.gpo.gov/fdsys/pkg/BILLS-114hr4752ih/pdf/BILLS-114hr4752ih.pdf

H.R. 4752 Space Exploration, Development, and Settlement Act of 2016 – March 16, 2016

A BILL To require the National Aeronautics and Space Administration to investigate and promote the exploration and development of space leading to human settlements beyond Earth, and for other purposes.

Maybe Dana Rorhabacher will figure out that science works! Even science he doesn’t like.

What he really needs to do is force this at the NASA federal charter level.

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United Launch Alliance ULA Engineering Executive Brett Tobey – Resigned and or is Fired – Effective Immediately

by Tommy on 17/03/2016

http://spacenews.com/ula-intends-to-lower-its-costs-and-raise-its-cool-to-compete-with-spacex/

Wow. The cats are officially out of the bag.

Calling all cat herders!

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Shock Compression Phase Diagram of Diamond Refined

by Tommy on 16/03/2016

http://www.nature.com/ncomms/2016/160314/ncomms10970/full/ncomms10970.html

Nanosecond formation of diamond and lonsdaleite by shock compression of graphite, D. Kraus, A. Ravasio, M. Gauthier, D. O. Gericke, J. Vorberger, S. Frydrych, J. Helfrich, L. B. Fletcher, G. Schaumann, B. Nagler, B. Barbrel, B. Bachmann, E. J. Gamboa, S. Göde, E. Granados, G. Gregori, H. J. Lee, P. Neumayer, W. Schumaker, T. Döppner, R. W. Falcone, S. H. Glenzer and M. Roth, Nature Communications, 7, 10970 (14 March 2016), doi:10.1038/ncomms10970

The shock-induced transition from graphite to diamond has been of great scientific and technological interest since the discovery of microscopic diamonds in remnants of explosively driven graphite. Furthermore, shock synthesis of diamond and lonsdaleite, a speculative hexagonal carbon polymorph with unique hardness, is expected to happen during violent meteor impacts. Here, we show unprecedented in situ X-ray diffraction measurements of diamond formation on nanosecond timescales by shock compression of pyrolytic as well as polycrystalline graphite to pressures from 19 GPa up to 228 GPa. While we observe the transition to diamond starting at 50 GPa for both pyrolytic and polycrystalline graphite, we also record the direct formation of lonsdaleite above 170 GPa for pyrolytic samples only. Our experiment provides new insights into the processes of the shock-induced transition from graphite to diamond and uniquely resolves the dynamics that explain the main natural occurrence of the lonsdaleite crystal structure being close to meteor impact sites.

So lonsdaleite is back yet again, apparently.

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Quantum Electrodynamics Simulation by Superconducting Transmission Line Resonators

by Tommy on 16/03/2016

http://arxiv.org/abs/1603.04686

Zi-He Yang, Yan-Pu Wang, Zheng-Yuan Xue, Wan-Li Yang, Yong Hu, Jin-Hua Gao and Ying Wu (15 March 2016)

The concept of flat band plays an important role in strongly-correlated many-body physics. However, the demonstration of the flat band physics is highly nontrivial due to intrinsic limitations in conventional condensed matter materials. Here we propose a circuit quantum electrodynamics simulator of the 2D Lieb lattice exhibiting a flat middle band. By exploiting the simple parametric conversion method, we design a photonic Lieb lattice with in situ tunable hopping strengths in a 2D array of coupled superconducting transmission line resonators. Moreover, the flexibility of our proposal enables the immediate incorporation of both the artificial gauge field and the strong photon-photon interaction in a time- and site-resolved manner. To unambiguously demonstrate the synthesized flat band, we further investigate the observation of the flat band localization of microwave photons through the pumping and the steady-state measurements of only few sites on the lattice. Requiring only current level of technique and being robust against imperfections in realistic circuits, our scheme can be readily tested in experiments and may pave a new way towards the future realization of exotic photonic quantum Hall fluids including anomalous quantum Hall effect and bosonic fractional quantum Hall states without magnetic fields.

Just the other day we get a mathematical theory, now they intend to simulate it.

That was fast.

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