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lattice degeneration

Jung-Wan Ryu, Nojoon Myoung, Hee Chul Park
We demonstrate mesoscopic transport through quantum states in quasi-1D lattices maintaining the combination of parity and time-reversal symmetries by controlling energy gain and loss. We investigate the phase diagram of the non-Hermitian system where transitions take place between unbroken and broken [Formula: see text]-symmetric phases via exceptional points. Quantum transport in the lattice is measured only in the unbroken phases in the energy band-but not in the broken phases. The broken phase allows for spontaneous symmetry-broken states where the cross-stitch lattice is separated into two identical single lattices corresponding to conditionally degenerate eigenstates...
August 18, 2017: Scientific Reports
M Sacchi, P Singh, D M Chisnall, D J Ward, A P Jardine, W Allison, J Ellis, H Hedgeland
We use helium spin-echo spectroscopy (HeSE) to investigate the dynamics of the diffusion of benzene adsorbed on Cu(111). The results of these measurements show that benzene moves on the surface through an activated jump-diffusion process between the adsorption sites on a Bravais lattice. Density Functional Theory (DFT) calculations with van der Waals (vdW) corrections help us understand that the molecule diffuses by jumping through non-degenerate hollow sites. The results of the calculations shed light on the nature of the binding interaction between this prototypical aromatic molecule and the metallic surface...
August 2, 2017: Faraday Discussions
Nicolas A Yannuzzi, Jonathan S Chang, Gary C Brown, William E Smiddy
PURPOSE: To evaluate the costs and cost-utility of examination for posterior vitreous detachment (PVD) and treatment of associated pathology, and of managing various other peripheral retinal disorders to prevent retinal detachment (RD). DESIGN: A decision analysis model of cost-utility. PARTICIPANTS: There were no participants. METHODS: Published retrospective data on the natural course of PVD, retinal tears, and lattice degeneration were used to quantitate the visual benefits of examination and treatment...
July 18, 2017: Ophthalmology
Wenjian Hu, Rajiv R P Singh, Richard T Scalettar
We apply unsupervised machine learning techniques, mainly principal component analysis (PCA), to compare and contrast the phase behavior and phase transitions in several classical spin models-the square- and triangular-lattice Ising models, the Blume-Capel model, a highly degenerate biquadratic-exchange spin-1 Ising (BSI) model, and the two-dimensional XY model-and we examine critically what machine learning is teaching us. We find that quantified principal components from PCA not only allow the exploration of different phases and symmetry-breaking, but they can distinguish phase-transition types and locate critical points...
June 2017: Physical Review. E
Xi-Wang Luo, Xingxiang Zhou, Jin-Shi Xu, Chuan-Feng Li, Guang-Can Guo, Chuanwei Zhang, Zheng-Wei Zhou
All-optical photonic devices are crucial for many important photonic technologies and applications, ranging from optical communication to quantum information processing. Conventional design of all-optical devices is based on photon propagation and interference in real space, which may rely on large numbers of optical elements, and the requirement of precise control makes this approach challenging. Here we propose an unconventional route for engineering all-optical devices using the photon's internal degrees of freedom, which form photonic crystals in such synthetic dimensions for photon propagation and interference...
July 14, 2017: Nature Communications
Giles Kagmeni, Georges Nguefack-Tsague, Steve Robert Ebana Mvogo, Come Ebana Mvogo
BACKGROUND: The purpose of this prospective, noncomparative consecutive study was to examine active and retired amateur boxers in order to evaluate the nature and incidence of ocular pathologic conditions related to the boxing practice. RESULTS: A total of 35 boxers were included in this study. The mean age of the boxers was 28.09±7.57 years (range 18-52 years). Sixteen (45.7%) boxers had >5 years of boxing experience. Fifteen (42.85%) of the boxers reported wearing protective equipment in the bouts and sparring rounds...
2017: Clinical Ophthalmology
Chengyong Zhong, Yuanping Chen, Zhi-Ming Yu, Yuee Xie, Han Wang, Shengyuan A Yang, Shengbai Zhang
Carbon, the basic building block of our universe, enjoys a vast number of allotropic structures. Owing to its bonding characteristic, most carbon allotropes possess the motif of hexagonal rings. Here, with first-principles calculations, we discover a new metastable three-dimensional carbon allotrope entirely composed of pentagon rings. The unique structure of this Pentagon Carbon leads to extraordinary electronic properties, making it a cornucopia of emergent topological fermions. Under lattice strain, Pentagon Carbon exhibits topological phase transitions, generating a series of novel quasiparticles, from isospin-1 triplet fermions to triply degenerate fermions and further to Hopf-link Weyl-loop fermions...
June 5, 2017: Nature Communications
Sera Kim, Seunghyun Song, Jongho Park, Ho Sung Yu, Suyeon Cho, Dohyun Kim, Jaeyoon Baik, Duk-Hyun Choe, K J Chang, Young Hee Lee, Sung Wng Kim, Heejun Yang
Doping two-dimensional (2D) semiconductors beyond their degenerate levels provides the opportunity to investigate extreme carrier density-driven superconductivity and phase transition in 2D systems. Chemical functionalization and the ionic gating have achieved the high doping density, but their effective ranges have been limited to ∼1 nm, which restricts the use of highly doped 2D semiconductors. Here, we report on electron diffusion from the 2D electride [Ca2N](+)·e(-) to MoTe2 over a distance of 100 nm from the contact interface, generating an electron doping density higher than 1...
June 14, 2017: Nano Letters
Arjun Kalra, Patrick Tishmack, Joseph W Lubach, Eric J Munson, Lynne S Taylor, Stephen R Byrn, Tonglei Li
Despite numerous challenges in their theoretical description and practical implementation, amorphous drugs are of growing importance to the pharmaceutical industry. One such challenge is to gain molecular level understanding of the propensity of a molecule to form and remain as a glassy solid. In this study, a series of structurally similar diarylamine compounds was examined to elucidate the role of supramolecular aggregation on crystallization kinetics from supercooled liquid state. The structural similarity of the compounds makes it easier to isolate the molecular features that affect crystallization kinetics and glass forming ability of these compounds...
May 17, 2017: Molecular Pharmaceutics
Jing-Kai Qin, Wen-Zhu Shao, Cheng-Yan Xu, Yang Li, Dan-Dan Ren, Xiao-Guo Song, Liang Zhen
Substitutional doping of transition metal dichalcogenide two-dimensional materials has proven to be effective in tuning their intrinsic properties, such as band gap, transport characteristics, and magnetism. In this study, we realized substitutional doping of monolayer rhenium disulfide (ReS2) with Mo via chemical vapor deposition. Scanning transmission electron microscopy demonstrated that Mo atoms are successfully doped into ReS2 by substitutionally replacing Re atoms in the lattice. Electrical measurements revealed the degenerate p-type semiconductor behavior of Mo-doped ReS2 field effect transistors, in agreement with density functional theory calculations...
May 1, 2017: ACS Applied Materials & Interfaces
M Schmidt, F M Zimmer, S G Magalhaes
The interplay between geometric frustration (GF) and bond disorder is studied in the Ising kagome lattice within a cluster approach. The model considers antiferromagnetic short-range couplings and long-range intercluster disordered interactions. The replica formalism is used to obtain an effective single cluster model from where the thermodynamics is analyzed by exact diagonalization. We found that the presence of GF can introduce cluster freezing at very low levels of disorder. The system exhibits an entropy plateau followed by a large entropy drop close to the freezing temperature...
April 26, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Kyounghwan Kim, Ashley DaSilva, Shengqiang Huang, Babak Fallahazad, Stefano Larentis, Takashi Taniguchi, Kenji Watanabe, Brian J LeRoy, Allan H MacDonald, Emanuel Tutuc
According to electronic structure theory, bilayer graphene is expected to have anomalous electronic properties when it has long-period moiré patterns produced by small misalignments between its individual layer honeycomb lattices. We have realized bilayer graphene moiré crystals with accurately controlled twist angles smaller than 1° and studied their properties using scanning probe microscopy and electron transport. We observe conductivity minima at charge neutrality, satellite gaps that appear at anomalous carrier densities for twist angles smaller than 1°, and tunneling densities-of-states that are strongly dependent on carrier density...
March 28, 2017: Proceedings of the National Academy of Sciences of the United States of America
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
Lukas Reichsöllner, Andreas Schindewolf, Tetsu Takekoshi, Rudolf Grimm, Hanns-Christoph Nägerl
We demonstrate a generally applicable technique for mixing two-species quantum degenerate bosonic samples in the presence of an optical lattice, and we employ it to produce low-entropy samples of ultracold ^{87}Rb^{133}Cs Feshbach molecules with a lattice filling fraction exceeding 30%. Starting from two spatially separated Bose-Einstein condensates of Rb and Cs atoms, Rb-Cs atom pairs are efficiently produced by using the superfluid-to-Mott insulator quantum phase transition twice, first for the Cs sample, then for the Rb sample, after nulling the Rb-Cs interaction at a Feshbach resonance's zero crossing...
February 17, 2017: Physical Review Letters
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
Miner Yuan, Xiaoyan Ding, Yu Yang, Fang Liu, Jiaqing Li, Xiaoling Liang, Xiongze Zhang, Andina Hu, Zijing Li, Zongyi Zhan, Lin Lu
PURPOSE: To report the clinical characteristics of the affected and fellow eyes in patients with familial exudative vitreoretinopathy-associated rhegmatogenous retinal detachment (FEVR-RRD). METHODS: This was a retrospective observational case series. The affected and fellow eyes were given complete examinations. The age, sex, clinical features of the affected eyes, and varied abnormalities of the fellow eyes were analyzed. RESULTS: Forty-three patients with FEVR-RRD were included...
March 2017: Retina
A M Martin, N G Marchant, D H J O'Dell, N G Parker
The experimental realization of quantum-degenerate Bose gases made of atoms with sizeable magnetic dipole moments has created a new type of fluid, known as a quantum ferrofluid, which combines the extraordinary properties of superfluidity and ferrofluidity. A hallmark of superfluids is that they are constrained to rotate through vortices with quantized circulation. In quantum ferrofluids the long-range dipolar interactions add new ingredients by inducing magnetostriction and instabilities, and also affect the structural properties of vortices and vortex lattices...
March 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Neesurg S Mehta, Nicolas A Yannuzzi, Ryan Young, Andrew J McClellan, Sarah P Read, Audina M Berrocal
A 12-year-old boy presented with a total rhegmatogenous retinal detachment and a giant retinal tear in the right eye. Clinical examination, optical coherence tomography, and fundus images showed an optically empty vitreous, lattice degeneration, and retinoschisis of the macula. Genetic testing revealed mutations in the COL2A1 and RS1 genes, confirming a dual diagnosis of Stickler syndrome and X-linked retinoschisis, respectively. This represents the first published account of a patient with both Stickler syndrome and X-linked retinoschisis...
January 1, 2017: Ophthalmic Surgery, Lasers & Imaging Retina
Stephan Rachel, Ilja Göthel, Daniel P Arovas, Matthias Vojta
Certain nonuniform strain applied to graphene flakes has been shown to induce pseudo-Landau levels in the single-particle spectrum, which can be rationalized in terms of a pseudomagnetic field for electrons near the Dirac points. However, this Landau level structure is, in general, approximate and restricted to low energies. Here, we introduce a family of strained bipartite tight-binding models in arbitrary spatial dimension d and analytically prove that their entire spectrum consists of perfectly degenerate pseudo-Landau levels...
December 23, 2016: Physical Review Letters
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