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"topological phase"

Yang-Yang Lv, Xiao Li, Bin-Bin Zhang, W Y Deng, Shu-Hua Yao, Y B Chen, Jian Zhou, Shan-Tao Zhang, Ming-Hui Lu, Lei Zhang, Mingliang Tian, L Sheng, Yan-Feng Chen
The asymmetric electron dispersion in type-II Weyl semimetal theoretically hosts anisotropic transport properties. Here, we observe the significant anisotropic Adler-Bell-Jackiw (ABJ) anomaly in the Fermi-level delicately adjusted WTe_{1.98} crystals. Quantitatively, C_{W}, a coefficient representing the intensity of the ABJ anomaly along the a and b axis of WTe_{1.98} are 0.030 and 0.051  T^{-2} at 2 K, respectively. We found that the temperature-sensitive ABJ anomaly is attributed to a topological phase transition from a type-II Weyl semimetal to a trivial semimetal, which is verified by a first-principles calculation using experimentally determined lattice parameters at different temperatures...
March 3, 2017: Physical Review Letters
Yang-Yang Lv, Lin Cao, Xiao Li, Bin-Bin Zhang, Kang Wang, Bin Pang, Ligang Ma, Dajun Lin, Shu-Hua Yao, Jian Zhou, Y B Chen, Song-Tao Dong, Wenchao Liu, Ming-Hui Lu, Yulin Chen, Yan-Feng Chen
Transition metal dichalcogenides (TMDs) WTe2 and MoTe2 with orthorhombic Td phase, being potential candidates as type-II Weyl semimetals, are attracted much attention recently. Here we synthesized a series of miscible Mo1-xWxTe2 single crystals by bromine vapor transport method. Composition-dependent X-ray diffraction and Raman spectroscopy, as well as composition and temperature-dependent resistivity prove that the tunable crystal structure (from hexagonal (2H), monoclinic (β) to orthorhombic (Td) phase) can be realized by increasing W content in Mo1-xWxTe2...
March 15, 2017: Scientific Reports
Luting Xu, Xinqi Li, Qingfeng Sun
The Josephson supercurrent through the hybrid Majorana--quantum dot--Majorana junction is investigated. We particularly analyze the effect of spin-selective coupling between the Majorana and quantum dot states, which emerges only in the topological phase and will influence the current through bent junctions and/or in the presence of magnetic fields in the quantum dot. We find that the characteristic behaviors of the supercurrent through this system are quite counterintuitive, remarkably differing from the resonant tunneling, e...
March 13, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Zhiwang Zhang, Qi Wei, Ying Cheng, Ting Zhang, Dajian Wu, Xiaojun Liu
The discovery of topological acoustics has revolutionized fundamental concepts of sound propagation, giving rise to strikingly unconventional acoustic edge modes immune to scattering. Because of the spinless nature of sound, the "spinlike" degree of freedom crucial to topological states in acoustic systems is commonly realized with circulating background flow or preset coupled resonator ring waveguides, which drastically increases the engineering complexity. Here we realize the acoustic pseudospin multipolar states in a simple flow-free symmetry-broken metamaterial lattice, where the clockwise (anticlockwise) sound propagation within each metamolecule emulates pseudospin down (pseudospin up)...
February 24, 2017: Physical Review Letters
Long Zhang, Fa Wang
A symmetry-protected topological phase has nontrivial surface states in the presence of certain symmetries, which can either be gapless or be degenerate. In this work, we study the physical consequence of such gapless surface states at the bulk quantum phase transition (QPT) that spontaneously breaks these symmetries. The two-dimensional Affleck-Kennedy-Lieb-Tasaki phase on a square lattice and its QPTs to Néel ordered phases are realized with the spin-1/2 Heisenberg model on a decorated square lattice. With large-scale quantum Monte Carlo simulations, we show that even though the bulk QPTs are governed by the conventional Landau phase transition theory, the gapless surface states induce unconventional universality classes of the surface critical behavior...
February 24, 2017: Physical Review Letters
Xiang-Fa Zhou, Xi-Wang Luo, Su Wang, Guang-Can Guo, Xingxiang Zhou, Han Pu, Zheng-Wei Zhou
We propose a scheme to simulate topological physics within a single degenerate cavity, whose modes are mapped to lattice sites. A crucial ingredient of the scheme is to construct a sharp boundary so that the open boundary condition can be implemented for this effective lattice system. In doing so, the topological properties of the system can manifest themselves on the edge states, which can be probed from the spectrum of an output cavity field. We demonstrate this with two examples: a static Su-Schrieffer-Heeger chain and a periodically driven Floquet topological insulator...
February 24, 2017: Physical Review Letters
L-Y Gan, R Wang, Y J Jin, D B Ling, J Z Zhao, W P Xu, J F Liu, H Xu
Based on first-principles calculations, we report that external pressure can induce a topological phase transition in alkaline-earth hexaborides, XB6 (X = Ca, Sr, and Ba). It was revealed that XB6 are transformed from trivial semiconductors to topological node-line semimetals under moderate pressure when the spin-orbit coupling (SOC) is ignored. The band inversion between the B p-orbitals at the X point is responsible for the formation of node-line semimetals. Three node-line rings around the X point are protected by the combination of the time-reversal and spatial inversion symmetries, and drumhead surface bands are obtained in the interiors of the projected node-line rings...
March 8, 2017: Physical Chemistry Chemical Physics: PCCP
Feng Liu, Katsunori Wakabayashi
We present a two-dimensional (2D) lattice model that exhibits a nontrivial topological phase in the absence of the Berry curvature. Instead, the Berry connection provides the topological nontrivial phase in the model, whose integration over the momentum space, the so-called 2D Zak phase, yields a fractional wave polarization in each direction. These fractional wave polarizations manifest themselves as degenerated edge states with opposite parities in the model.
February 17, 2017: Physical Review Letters
I A Nechaev, S V Eremeev, E E Krasovskii, P M Echenique, E V Chulkov
The quantum spin Hall insulators predicted ten years ago and now experimentally observed are instrumental for a break- through in nanoelectronics due to non-dissipative spin-polarized electron transport through their edges. For this transport to persist at normal conditions, the insulators should possess a sufficiently large band gap in a stable topological phase. Here, we theoretically show that quantum spin Hall insulators can be realized in ultra-thin films constructed from a trivial band insulator with strong spin-orbit coupling...
March 2, 2017: Scientific Reports
Xiang Yuan, Peihong Cheng, Longqiang Zhang, Cheng Zhang, Junyong Wang, Yanwen Liu, Qingqing Sun, Peng Zhou, David Wei Zhang, Zhigao Hu, Xiangang Wan, Hugen Yan, Zhiqiang Li, Faxian Xiu
Three-dimensional topological Dirac semimetals have hitherto stimulated unprecedented research interests as a new class of quantum materials. Breaking certain types of symmetries has been proposed to enable the manipulation of Dirac fermions, and that was soon realized by external modulations such as magnetic fields. However, an intrinsic manipulation of Dirac states, which is more efficient and desirable, remains a significant challenge. Here, we report a systematic study of quasi-particle dynamics and band evolution in Cd3As2 thin films with controlled chromium (Cr) doping by both magneto-infrared spectroscopy and electrical transport...
March 2, 2017: Nano Letters
Svitlana Kondovych, Igor Luk'yanchuk, Tatyana I Baturina, Valerii M Vinokur
The two-dimensional (2D) logarithmic character of Coulomb interaction between charges and the resulting logarithmic confinement is a remarkable inherent property of high dielectric constant (high-κ) thin films with far reaching implications. Most and foremost, this is the charge Berezinskii-Kosterlitz-Thouless transition with the notable manifestation, low-temperature superinsulating topological phase. Here we show that the range of the confinement can be tuned by the external gate electrode and unravel a variety of electrostatic interactions in high-k films...
February 20, 2017: Scientific Reports
Maria Barrio, Judit Huguet, Ivo B Rietveld, Benoît Robert, René Céolin, Josep-Lluis Tamarit
Understanding the polymorphic behavior of active pharmaceutical ingredients is important for formulation purposes and regulatory reasons. Metacetamol is an isomer of paracetamol and it similarly exhibits polymorphism. In the present article, it has been found that one of the polymorphs of metacetamol is only stable under increased pressure, which has led to the conclusion that metacetamol like paracetamol is a monotropic system under ordinary (= laboratory) conditions and that it becomes enantiotropic under pressure with the I-II-L triple point coordinates for metacetamol TI-II-L = 535 ± 10 K and PI-II-L = 692 ± 70 MPa...
February 10, 2017: Journal of Pharmaceutical Sciences
Maciej Bieniek, Tomasz Woźniak, Paweł Potasz
We investigate electronic and transport properties of bismuth (111) bilayer in the context of stability of its topological properties against different perturbations. The effects of spin-orbit coupling variations, geometry relaxation and an interaction with a substrate are considered. Transport properties are studied in the presence of Anderson disorder. Band structure calculations are performed within multi-orbital tight-binding model and density functional theory methods. A band inversion process in bismuth (111) infinite bilayer and an evolution of edge states dispersion in ribbons as a function of spin-orbit coupling strength are analyzed...
February 6, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
R Céolin, I B Rietveld
Cimetidine is a histamine H2-receptor antagonist used against peptic ulcers. It is known to exhibit crystalline polymorphism. Forms A and D melt within 0.35 degrees from each other and the enthalpies of fusion are similar as well. The present paper demonstrates how to construct a pressure-temperature phase diagram with only calorimetric and volumetric data available. The phase diagram provides the stability domains and the phase equilibria for the phases A, D, the liquid and the vapor. Cimetidine is overall monotropic with form D the only stable solid phase...
March 2017: Annales Pharmaceutiques Françaises
Yunhua Wang, Yulan Liu, Biao Wang
Periodically driven nontrivial quantum states open another door to engineer topological phases in solid systems by light. Here we show, based on the Floquet-Bloch theory, that the on-resonant linearly and circularly polarized infrared light brings in the exotic Floquet quantum spin Hall state and half-metal in two-dimensional Metal-organic frameworks (2D MOFs) because of the unbroken and broken time-reversal symmetry, respectively. We also observe that the off-resonant light triggers topological quantum phase transitions and induces semimetals with pseudospin-1 Dirac-Weyl fermions via the photon-dressed topological band structures of 2D MOFs...
January 30, 2017: Scientific Reports
Kai-Wei Chang, Wei Ji, Chao-Cheng Kaun
The way in which states of a topological insulator (TI) transform from monolayer to bulk is an important issue for applications in spintronics. However, unlike graphite, most layered materials are difficult to exfoliate. Using first-principles calculations, we predict that thallium selenide (TlSe) will be a layered TI with rather weak interlayer coupling and thus it should be exfoliated easily. The evolution of the topological states can also be driven by doping with indium (In) atoms or applying lateral strains...
February 1, 2017: Physical Chemistry Chemical Physics: PCCP
Xiaoming Cai
We study the competition of disorder and superconductivity for a generalized Kitaev model in incommensurate potentials. The generalized Kitaev model describes one dimensional spinless fermions with long-range p-wave superconducting pairing, which decays with distance l as a power law  ∼[Formula: see text]. We focus on the transition from the topological superconducting phase to the topologically trivial Anderson localized phase, and effects of the exponent α on this phase transition. In the topological superconducting phase, for a system under open boundary condition the amplitude of zero-mode Majorana fermion has a hybrid exponential-algebraic decay as the distance increases from the edge...
March 22, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
M Hyla
Network-forming As2(S/Se)m nanoclusters are employed to recognize expected variations in a vicinity of some remarkable compositions in binary As-Se/S glassy systems accepted as signatures of optimally constrained intermediate topological phases in earlier temperature-modulated differential scanning calorimetry experiments. The ab initio quantum chemical calculations performed using the cation-interlinking network cluster approach show similar oscillating character in tendency to local chemical decomposition but obvious step-like behavior in preference to global phase separation on boundary chemical compounds (pure chalcogen and stoichiometric arsenic chalcogenides)...
December 2017: Nanoscale Research Letters
Morten Amundsen, Jabir Ali Ouassou, Jacob Linder
Multiterminal Josephson junctions have recently been proposed as a route to artificially mimic topological matter with the distinct advantage that its properties can be controlled via the superconducting phase difference, giving rise to Weyl points in 4-terminal geometries. A key goal is to accurately determine when the system makes a transition from a gapped to non-gapped state as a function of the phase differences in the system, the latter effectively playing the role of quasiparticle momenta in conventional topological matter...
January 17, 2017: Scientific Reports
Sergey Kruk, Alexey Slobozhanyuk, Denitza Denkova, Alexander Poddubny, Ivan Kravchenko, Andrey Miroshnichenko, Dragomir Neshev, Yuri Kivshar
Recently introduced field of topological photonics aims to explore the concepts of topological insulators for novel phenomena in optics. Here polymeric chains of subwavelength silicon nanodisks are studied and it is demonstrated that these chains can support two types of topological edge modes based on magnetic and electric Mie resonances, and their topological properties are fully dictated by the spatial arrangement of the nanoparticles in the chain. It is observed experimentally and described how theoretically topological phase transitions at the nanoscale define a change from trivial to nontrivial topological states when the edge mode is excited...
January 12, 2017: Small
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