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Journal of Physics. Condensed Matter: An Institute of Physics Journal

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https://www.readbyqxmd.com/read/28207420/temperature-dependent-collective-effects-for-silicene-and-germanene
#1
Andrii Iurov, Godfrey Gumbs, Danhong Huang
We have numerically calculated electron exchange and correlation energies and dynamical polarization functions for recently discovered silicene, germanene and other buckled honeycomb lattices at various temperatures. We have compared the dependence of these energies on the chemical potential, field-induced gap and temperature and we have concluded that in many cases they behave qualitatively in a similar way, i.e. increasing with the doping, decreasing significantly at elevated temperatures, and displaying different dependences on the asymmetry gap at various temperatures...
February 16, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28199222/liquid-crystals-in-micron-scale-droplets-shells-and-fibers
#2
Martin Urbanski, Catherine G Reyes, JungHyun Noh, Anshul Sharma, Yong Geng, Venkata Subba Rao Jampani, Jan P F Lagerwall
The extraordinary responsiveness and large diversity of self-assembled structures of liquid crystals are well documented and they have been extensively used in devices like displays. For long, this application route strongly influenced academic research, which frequently focused on the performance of liquid crystals in display-like geometries, typically between flat, rigid substrates of glass or similar solids. Today a new trend is clearly visible, where liquid crystals confined within curved, often soft and flexible, interfaces are in focus...
February 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28199221/on-the-high-pressure-phase-stability-and-elastic-properties-of-%C3%AE-titanium-alloys
#3
Dean Smith, Oliver Joris, Ananthi Sankaran, Hannah Weekes, Dan Bull, Timothy Prior, David Dye, Daniel Errandonea, John Proctor
We have studied the compressibility and stability of different β-titanium alloys at high pressure, including binary Ti-Mo, Ti-24Nb-4Zr-8Sn (Ti2448) and Ti-36Nb-2Ta-0.3O (gum metal). We observed stability of the β phase in these alloys to 40 GPa, well into the ω phase region in the P-T diagram of pure titanium. Gum metal was pressurised above 70 GPa and forms a phase with a crystal structure similar to the η phase of pure Ti. The bulk moduli determined for the different alloys range from 97 ± 3 GPa (Ti2448) to 124 ± 6 GPa (Ti-16...
February 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28199220/critical-analysis-of-soft-point-contact-andreev-reflection-spectra-between-superconducting-films-and-pressed-in
#4
Pradnya Parab, Prashant Chauhan, H Muthurajan, Sangita Bose
We present a critical analysis of an alternative technique of point contact Andreev reflection (PCAR) spectroscopy used to extract energy resolved information of superconductors which is based on making 'soft-contacts' between superconductors and indium. This technique is not sensitive to mechanical vibrations and hence can be used in a cryogen free platform increasing its accessibility to users having no access to cryogenic liquids. Through our experiments on large number of superconducting films we show that the PCAR spectra below the T c of In show sub-harmonic gap structures consistent with the theory of multiple Andreev reflection (MAR) and a zero bias conductance (ZBC) anomaly associated with the Josephson supercurrent...
February 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28198355/in-situ-spectroscopy-of-ligand-exchange-reactions-at-the-surface-of-colloidal-gold-and-silver-nanoparticles
#5
Rebecca Dinkel, Wolfgang Peukert, Björn Braunschweig
Gold and silver nanoparticles with their tunable optical and electronic properties are of great interest for a wide range of applications. Often the ligands at the surface of the nanoparticles have to be exchanged in a second step after particle formation in order to obtain a desired surface functionalization. For many techniques, this process is not accessible in situ. In this review, we present second-harmonic scattering (SHS) as an inherently surface sensitive and label-free optical technique to probe the ligand exchange at the surface of colloidal gold and silver nanoparticles in situ and in real time...
February 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28198353/adsorption-and-migration-of-single-metal-atoms-on-the-calcite-10-4-surface
#6
H Pinto, V Haapasilta, M Lokhandwala, S Öberg, Adam S Foster
Transition metal atoms are one of the key ingredients in the formation of functional 2D metal organic coordination networks. Additionally, the co-deposition of metal atoms can play an important role in anchoring the molecular structures to the surface at room temperature. To gain control of such processes requires the understanding of adsorption and diffusion properties of the different transition metals on the target surface. Here, we used density functional theory to investigate the adsorption of 3d (Ti, Cr, Fe, Ni, Cu), 4d (Zr, Nb, Mo, Pd, Ag) and 5d (Hf, W, Ir, Pt, Au) transition metal adatoms on the insulating calcite (10...
February 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28198352/origin-of-the-apparent-delocalization-of-the-conduction-band-in-high-mobility-amorphous-semiconductors
#7
Albert de Jamblinne de Meux, Geoffrey Pourtois, Jan Genoe, Paul Heremans
In this paper, we show that the apparent delocalization of the conduction band reported from first-principles simulations for the high-mobility amorphous oxide semiconductor InGaZnO<sub>4</sub> (a-IGZO) is an artifact induced by the periodic conditions imposed to the model. Given a sufficiently large unit-cell dimension (over 40Å), the conduction band becomes localized. Such model size is up to four times the size of commonly used models for the study of a-IGZO. This finding challenges the analyses done so far on the nature of the defects and on the interpretation of numerous electrical measurements...
February 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28195564/time-dependent-wave-packet-simulations-of-transport-through-aharanov-bohm-rings-with-an-embedded-quantum-dot
#8
Christoph Kreisbeck, Tobias Kramer, Rafael A Molina
We have performed time-dependent wave packet simulations of realistic Aharonov-Bohm (AB) devices with a quantum dot embedded in one of the arms of the interferometer. The AB ring can function as a measurement device for the intrinsic transmission phase through the quantum dot, however, care has to be taken in analyzing the influence of scattering processes in the junctions of the interferometer arms. We consider a harmonic quantum dot and show how the Darwin-Fock spectrum emerges as a unique pattern in the interference fringes of the AB oscillations...
February 14, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28195563/electron-dynamics-in-graphene-with-spin-orbit-couplings-and-periodic-potentials
#9
Ranjani Seshadri, Diptiman Sen
We use both continuum and lattice models to study the energy-momentum dispersion and the dynamics of a wave packet for an electron moving in graphene in the presence of spin-orbit couplings and either a single potential barrier or a periodic array of potential barriers. Both Kane-Mele and Rashba spin-orbit couplings are considered. A number of special things occur when the Kane-Mele and Rashba couplings are equal in magnitude. In the absence of a potential, the dispersion then consists of both massless Dirac and massive Dirac states...
February 14, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28195076/energy-level-alignment-at-planar-organic-heterojunctions-influence-of-contact-doping-and-molecular-orientation
#10
Andreas Opitz
Planar organic heterojunctions are widely used in photovoltaic cells, light-emitting diodes, and bilayer field-effect transistors. The energy level alignment in the devices plays an important role in obtaining the aspired gap arrangement. Additionally, the π-orbital overlap between the involved molecules defines e.g. the charge-separation efficiency in solar cells due to charge-transfer effects. To account for both aspects, direct/inverse photoemission spectroscopy and near edge x-ray absorption fine structure spectroscopy were used to determine the energy level landscape and the molecular orientation at prototypical planar organic heterojunctions...
February 14, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28192286/superconducting-properties-of-the-s-%C3%A2-wave-state-fe-based-superconductors
#11
Yunkyu Bang, G R Stewart
Although the pairing mechanism of Fe-based superconductors (FeSCs) has not yet been settled with consensus with regard to the pairing symmetry and the superconducting (SC) gap function, the vast majority of experiments support the existence of spin-singlet sign-changing s-wave SC gaps on multi-bands ([Formula: see text]-wave state). This multi-band [Formula: see text]-wave state is a very unique gap state per se and displays numerous unexpected novel SC properties, such as a strong reduction of the coherence peak, non-trivial impurity effects, nodal-gap-like nuclear magnetic resonance signals, various Volovik effects in the specific heat (SH) and thermal conductivity, and anomalous scaling behaviors with a SH jump and condensation energy versus T c, etc...
February 13, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28192279/alm2b2-m-cr-mn-fe-co-ni-a-group-of-nanolaminated-materials
#12
Krisztina Kádas, Diana Iusan, Johan Hellsvik, Johan Cedervall, Pedro Berastegui, Martin Sahlberg, Ulf Jansson, Olle Eriksson
Combining theory with experiments, we study the phase stability, elastic properties, electronic structure and hardness of layered ternary borides AlCr2B2, AlMn2B2, AlFe2B2, AlCo2B2, and AlNi2B2. We find that the first three borides of this series are stable phases, while AlCo2B2 and AlNi2B2 are metastable. We show that the elasticity increases in the boride series, and predict that AlCr2B2, AlMn2B2, and AlFe2B2 are more brittle, while AlCo2B2 and AlNi2B2 are more ductile. We propose that the elasticity of AlFe2B2 can be improved by alloying it with cobalt or nickel, or a combination of them...
February 13, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28186495/effect-of-interface-on-epitaxy-and-magnetism-in-h-rfeo3-fe3o4-al2o3-films-r-lu-yb
#13
Xiaozhe Zhang, Yuewei Yin, Sen Yang, Zhimao Yang, Xiaoshan Xu
We have carried out the growth of h-RFeO3 (001) (R=Lu, Yb) thin films on Fe3O4 (111)/Al2O3 (001) substrates, and studied the effect of the h-RFeO3 (001)/Fe3O4 (111) interfaces on the epitaxy and magnetism. The observed epitaxial relations between h-RFeO3 and Fe3O4 indicates an unusual matching of Fe sub-lattices rather than a matching of O sub-lattices. The out-of-plane direction was found to be the easy magnetic axis for h-YbFeO3 (001) but the hard axis for Fe3O4 (111) in the h-YbFeO3 (001)/Fe3O4 (111)/Al2O3 (001) films, suggesting a perpendicular magnetic alignment at the h-YbFeO3 (001)/Fe3O4 (111) interface...
February 10, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28181915/interlayer-vacancy-defects-in-aa-stacked-bilayer-graphene-density-functional-theory-predictions
#14
Amanda Vuong, Tom Trevethan, Christopher Latham, Chris Ewels, Doğan Erbahar, Patrick Briddon, Mark Rayson, Malcolm Heggie
AA-stacked graphite and closely related structures, where carbon atoms are located in registry in adjacent graphene layers, are a feature of graphitic systems including twisted and folded bilayer graphene, and turbostratic graphite. We present the results of <i>ab initio</i> density functional theory calculations performed to investigate the complexes that are formed from the binding of vacancy defects across neighbouring layers in AA-stacked bilayers. As with AB stacking, the carbon atoms surrounding lattice vacancies can form interlayer structures with sp<sup>2</sup> bonding that are lower in energy than in-plane reconstructions...
February 9, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28181914/importance-of-bulk-states-for-the-electronic-structure-of-semiconductor-surfaces-implications-for-finite-slabs
#15
Keisuke Sagisaka, Jun Nara, David Bowler
We investigate the influence of slab thickness on the electronic structure of the Si(100)-p(2x2) surface in density functional theory (DFT) calculations, considering both density of states and band structure. Our calculations, with slab thicknesses of up to 78 atomic layers, reveal that the slab thickness profoundly affects the surface band structure, particularly the dangling bond states of the silicon dimers near the Fermi level. We find that, to precisely reproduce the surface bands, the slab thickness needs to be large enough to completely converge the bulk bands in the slab...
February 9, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28181913/simulation-on-the-electronic-wave-packet-cyclotron-motion-in-a-weyl-semimetal-slab
#16
Haibo Yao, Mingfeng Zhu, Liwei Jiang, Yisong Zheng
We perform a numerical simulation on time evolution of electronic wave packet in a Weyl semimetal(WSM) slab driven by a magnetic field. We find that the evolution trajectory of the wave packet depends sensitively on its initial spin state. Only the initial spin state being identical to that of the Fermi arc state at the surface it localized, does the wave packet evolution demonstrate the characteristic cyclotron orbit of WSM predicted previously from a semiclassical viewpoint. By analyzing the eigen-expansion of the electronic wave packet, we find the chiral Landau Levels(LLs) of the WSM slab, as an ingredient of the wave packet, is responsible for establishing the characteristic cyclotron orbit of Weyl semimetal...
February 9, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28177926/self-consistent-mean-field-theory-studies-of-the-thermodynamics-and-quantum-spin-dynamics-of-magnetic-skyrmions
#17
Robert Wieser
A self-consistent mean field theory is introduced and used to investigate the thermodynamics and spin dynamics of an S = 1 quantum spin system with a magnetic Skyrmion. The temperature dependence of the Skyrmion profile as well as the phase diagram are calculated. In addition, the spin dynamics of a magnetic Skyrmion is described by solving the time dependent Schrödinger equation with additional damping term. The Skyrmion annihilation process driven by an electric field is used to compare the trajectories of the quantum mechanical simulation with a semi-classical description for the spin expectation values using a differential equation similar to the classical Landau-Lifshitz-Gilbert equation...
February 8, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28177296/a-first-principles-model-for-anomalous-segregation-in-dilute-ternary-tungsten-rhenium-vacancy-alloys
#18
Jan Wrobel, Duc Nguyen-Manh, Sergei Dudarev, Krzysztof Kurzydłowski
The occurrence of segregation in dilute alloys under irradiation is a highly unusual phenomenon that has recently attracted attention, simulated by the interest in the fundamental properties of alloys as well as by applications. The fact that solute atoms segregate in alloys that, according to equilibrium thermodynamics, should exhibit full solubility, has significant practical implications, as the formation of precipitates strongly affects physical and mechanical properties. A lattice Hamiltonian model, generalizing so-called "ABV" Ising model and including collective many-body inter-atomic interactions, has been developed to treat rhenium solute atoms and vacancies in tungsten as components of a ternary alloy...
February 8, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28176680/high-temperature-superconductivity-in-one-unit-cell-fese-films
#19
Ziqiao Wang, Chaofei Liu, Yi Liu, Jian Wang
Since the dramatic interface enhancement of superconducting transition temperature (Tc) was reported in one unit-cell FeSe film grown on SrTiO3 substrate (1-UC FeSe/STO) by molecular beam epitaxy (MBE), related research on this system has become a new frontier in condensed matter physics. In this paper, we present a brief review on this rapidly developing field, mainly focusing on the superconducting properties of 1-UC FeSe/STO. Experimental evidences for the high-temperature superconductivity in 1-UC FeSe/STO, including the direct evidences revealed by transport and diamagnetic measurements, and other evidences from scanning tunneling microscope (STM) and angle-resolved photoemission spectroscopy (ARPES), are overviewed...
February 8, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28170355/does-a-network-structure-exist-in-molecular-liquid-sni-sub-4-sub-and-gei-sub-4-sub
#20
Takahiro Sakagami, Kazuhiro Fuchizaki
The existence of a network structure consisting of electrically neutral tetrahedral molecules in liquid SnI<sub>4</sub> and GeI<sub>4</sub> at ambient pressure was examined. The liquid structures employed for the examination were obtained from a reverse Monte Carlo analysis. The structures were physically interpreted by introducing an appropriate intermolecular interaction. A "bond" was then defined as an intermolecular connection that minimizes the energy of intermolecular interaction...
February 7, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
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