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lattice degeneration

Sera Kim, Seunghyun Song, Jongho Park, Ho Sung Yu, Suyeon Cho, Dohyun Kim, Jaeyoon Baik, Duk-Hyun Choe, Kee Joo 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...
May 10, 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
Gaute Otnes, Magnus Heurlin, Xulu Zeng, Magnus T Borgström
Semiconductor nanowires are versatile building blocks for optoelectronic devices, in part because nanowires offer an increased freedom in material design due to relaxed constraints on lattice matching during the epitaxial growth. This enables the growth of ternary alloy nanowires in which the bandgap is tunable over a large energy range, desirable for optoelectronic devices. However, little is known about the effects of doping in the ternary nanowire materials, a prerequisite for applications. Here we present a study of p-doping of InxGa1-xP nanowires and show that the growth dynamics are strongly affected when diethylzinc is used as a dopant precursor...
January 5, 2017: Nano Letters
Nyayabanta Swain, Pinaki Majumdar
The checkerboard lattice, with alternating 'crossed' plaquettes, serves as the two dimensional analog of the pyrochlore lattice. The corner sharing plaquette structure leads to a hugely degenerate ground state, and no magnetic order, for classical spins with short range antiferromagnetic interaction. For the half-filled Hubbard model on this structure, however, we find that the Mott insulating phase involves virtual electronic processes that generate longer range and multispin couplings. These couplings lift the degeneracy, selecting a 'flux like' state in the Mott insulator...
March 1, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Brijesh Takkar, Shorya Azad, Adarsh Shashni, Amar Pujari, Indrish Bhatia, Rajvardhan Azad
AIM: To evaluate the causes and associations of missed retinal breaks (MRBs) and posterior vitreous detachment (PVD) in patients with rhegmatogenous retinal detachment (RRD). METHODS: Case sheets of patients undergoing vitreo retinal surgery for RRD at a tertiary eye care centre were evaluated retrospectively. Out of the 378 records screened, 253 were included for analysis of MRBs and 191 patients were included for analysis of PVD, depending on the inclusion criteria...
2016: International Journal of Ophthalmology
R P M J W Notermans, R J Rengelink, W Vassen
We observe a dramatic difference in optical line shapes of a ^{4}He Bose-Einstein condensate and a ^{3}He degenerate Fermi gas by measuring the 1557-nm 2 ^{3}S-2 ^{1}S magnetic dipole transition (8 Hz natural linewidth) in an optical dipole trap. The 15 kHz FWHM condensate line shape is only broadened by mean field interactions, whereas the degenerate Fermi gas line shape is broadened to 75 kHz FWHM due to the effect of Pauli exclusion on the spatial and momentum distributions. The asymmetric optical line shapes are observed in excellent agreement with line shape models for the quantum degenerate gases...
November 18, 2016: Physical Review Letters
Sangen Zhao, Yi Yang, Yaoguo Shen, Bingqing Zhao, Lina Li, Chengmin Ji, Zhenyue Wu, Daqiang Yuan, Zheshuai Lin, Maochun Hong, Junhua Luo
Nitrates have long been ignored for practical uses as nonlinear optical (NLO) materials because they are usually very easy to dissolve in water; despite this, the π-conjugated [NO3 ](-) is among the most desirable NLO-active structural units. The cooperation of three structural chromophores, namely, Bi3 O6 OH short chains with 6s(2) lone pair electrons, distorted TeO6 octahedra with d(10) electrons, and π-conjugated [NO3 ](-) triangles, generates a new nitrate NLO material, Bi3 TeO6 OH(NO3 )2 , which exhibits an enhanced phase-matchable NLO response of three times that of KH2 PO4 (3×KH2 PO4 ), exceeding those of most nitrate NLO materials...
January 9, 2017: Angewandte Chemie
Yann Perrin, Benjamin Canals, Nicolas Rougemaille
Artificial spin-ice systems are lithographically patterned arrangements of interacting magnetic nanostructures that were introduced as way of investigating the effects of geometric frustration in a controlled manner. This approach has enabled unconventional states of matter to be visualized directly in real space, and has triggered research at the frontier between nanomagnetism, statistical thermodynamics and condensed matter physics. Despite efforts to create an artificial realization of the square-ice model-a two-dimensional geometrically frustrated spin-ice system defined on a square lattice-no simple geometry based on arrays of nanomagnets has successfully captured the macroscopically degenerate ground-state manifold of the model...
December 15, 2016: Nature
Zhan Wu, Long Zhang, Wei Sun, Xiao-Tian Xu, Bao-Zong Wang, Si-Cong Ji, Youjin Deng, Shuai Chen, Xiong-Jun Liu, Jian-Wei Pan
Cold atoms with laser-induced spin-orbit (SO) interactions provide a platform to explore quantum physics beyond natural conditions of solids. Here we propose and experimentally realize two-dimensional (2D) SO coupling and topological bands for a rubidium-87 degenerate gas through an optical Raman lattice, without phase-locking or fine-tuning of optical potentials. A controllable crossover between 2D and 1D SO couplings is studied, and the SO effects and nontrivial band topology are observed by measuring the atomic cloud distribution and spin texture in momentum space...
October 7, 2016: Science
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