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lattice degeneration

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...
November 30, 2016: 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...
November 28, 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
A L Chernyshev, P A Maksimov
We demonstrate that interactions can substantially undermine the free-particle description of magnons in ferromagnets on geometrically frustrated lattices. The anharmonic coupling, facilitated by the Dzyaloshinskii-Moriya interaction, and a highly degenerate two-magnon continuum yield a strong, nonperturbative damping of the high-energy magnon modes. We provide a detailed account of the effect for the S=1/2 ferromagnet on the kagome lattice and propose further experiments.
October 28, 2016: Physical Review Letters
Martin Leder, Christopher Grossert, Lukas Sitta, Maximilian Genske, Achim Rosch, Martin Weitz
To describe a mobile defect in polyacetylene chains, Su, Schrieffer and Heeger formulated a model assuming two degenerate energy configurations that are characterized by two different topological phases. An immediate consequence was the emergence of a soliton-type edge state located at the boundary between two regions of different configurations. Besides giving first insights in the electrical properties of polyacetylene materials, interest in this effect also stems from its close connection to states with fractional charge from relativistic field theory...
October 21, 2016: Nature Communications
S S Naghavi, M Fabrizio, T Qin, E Tosatti
The quantum physics of ions and electrons behind low-energy spectra of strongly correlated molecular conductors, superconductors and Mott insulators is poorly known, yet fascinating especially in orbitally degenerate cases. The fulleride insulator Cs3C60 (A15), one such system, exhibits infrared (IR) spectra with low temperature peak features and splittings suggestive of static Jahn-Teller distortions with a breakdown of orbital symmetry in the molecular site. That is puzzling, since there is no detectable static distortion, and because the features and splittings disappear upon modest heating, which they should not...
October 14, 2016: Nanoscale
David J Mathew, Saurabh Kumar Sarma, Jennifer V Basaiawmoit
Lattice degeneration of the retina is not infrequently encountered on a dilated retinal examination and many of them do not need any intervention. We report a case of atypical lattice degeneration variant with peripheral retinal detachment. An asymptomatic 35-year-old lady with minimal refractive error was found to have extensive lattice degeneration, peripheral retinal detachment and fibrotic changes peripherally with elevation of retinal vessels on dilated retinal examination. There were also areas of white without pressure, chorioretinal scarring and retinal breaks...
July 2016: Journal of Clinical and Diagnostic Research: JCDR
W Zhu, Shou-Shu Gong, Tian-Sheng Zeng, Liang Fu, D N Sheng
Topological states of matter have been widely studied as being driven by an external magnetic field, intrinsic spin-orbital coupling, or magnetic doping. Here, we unveil an interaction-driven spontaneous quantum Hall effect (a Chern insulator) emerging in an extended fermion-Hubbard model on a kagome lattice, based on a state-of-the-art density-matrix renormalization group on cylinder geometry and an exact diagonalization in torus geometry. We first demonstrate that the proposed model exhibits an incompressible liquid phase with doublet degenerate ground states as time-reversal partners...
August 26, 2016: Physical Review Letters
Milton A Tumelero, Ricardo Faccio, Andre A Pasa
Bi2Se3 is a prominent narrow gap semiconductor with a rhombohedral crystal structure and potential applications in thermoelectric and spintronic technologies. Its electrical conduction is ruled by native point defects inducing an n-type degenerate behavior. Here, we present a first principles study of the point defects in Bi2Se3, focusing on the relevance of the interstitial sites. A density functional methodology was employed with van der Waals correction and spin-orbit coupling in order to achieve a better description of the defects...
October 26, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Gabriel Mazzucchi, Santiago F Caballero-Benitez, Igor B Mekhov
Ultracold atomic systems offer a unique tool for understanding behavior of matter in the quantum degenerate regime, promising studies of a vast range of phenomena covering many disciplines from condensed matter to quantum information and particle physics. Coupling these systems to quantized light fields opens further possibilities of observing delicate effects typical of quantum optics in the context of strongly correlated systems. Measurement backaction is one of the most funda- mental manifestations of quantum mechanics and it is at the core of many famous quantum optics experiments...
2016: Scientific Reports
Yasser Helmy Mohamed, Kozue Ono, Hirofumi Kinoshita, Masafumi Uematsu, Eiko Tsuiki, Azusa Fujikawa, Takashi Kitaoka
Aim. To investigate the anatomical success rates of pars plana vitrectomy (PPV) after primary rhegmatogenous retinal detachment (RRD). Methods. This retrospective study was conducted between December 2008 and October 2014 at Nagasaki University Hospital. The preoperative data recorded included the lens status, location of the retinal tear, whether a tear was visualized, presence of multiple tears, macula status, presence of peripheral lattice retinal degeneration, and best-corrected visual acuity (BCVA). The primary outcome measures were anatomical (primary and final) and functional success (visual acuity better than 6/60)...
2016: Journal of Ophthalmology
Rudro R Biswas, Dam Thanh Son
The quest for universal properties of topological phases is fundamentally important because these signatures are robust to variations in system-specific details. Aspects of the response of quantum Hall states to smooth spatial curvature are well-studied, but challenging to observe experimentally. Here we go beyond this prevailing paradigm and obtain general results for the response of quantum Hall states to points of singular curvature in real space; such points may be readily experimentally actualized. We find, using continuum analytical methods, that the point of curvature binds an excess fractional charge and sequences of quantum states split away, energetically, from the degenerate bulk Landau levels...
August 2, 2016: Proceedings of the National Academy of Sciences of the United States of America
Yi-Yang Sun, Shengbai Zhang
Bulk black phosphorus has two optical phonon modes labeled as Ag (2) and B2u, respectively, that are nearly degenerate in frequency. However, density functional theory calculations using local or semi-local functionals cannot reproduce this degeneracy. Here, we propose a hybrid functional approach aided by van der Waals (vdW) force fields, which can accurately describe the lattice dynamic and electronic properties of both bulk and few-layer black phosphorus (phosphorene). Using this approach we show that in bilayer phosphorene, the two Raman modes derived from the B2u and Ag (2) modes could exhibit strong resonance as a result of the accidental degeneracy so that both modes could be observed in Raman experiment...
July 14, 2016: Journal of Chemical Physics
A Abdel-Rehim, C Alexandrou, M Constantinou, K Hadjiyiannakou, K Jansen, Ch Kallidonis, G Koutsou, A Vaquero Avilés-Casco
We evaluate the light, strange, and charm scalar content of the nucleon using one lattice QCD ensemble generated with two degenerate light quarks with mass fixed to their physical value. We use improved techniques to evaluate the disconnected quark loops to sufficient accuracy to determine the strange and charm nucleon σ terms in addition to the light quark content σ_{πN}. We find σ_{πN}=37.2(2.6)(4.7/2.9)  MeV, σ_{s}=41.1(8.2)(7.8/5.8)  MeV, and σ_{c}=79(21)(12/8)  MeV, where the first error is statistical and the second is the systematic error due to the determination of the lattice spacing, the assessment of finite volume, and residual excited state effects...
June 24, 2016: Physical Review Letters
Johan Carlström, Nikolay Prokof'ev, Boris Svistunov
We study the propagation of a hole in degenerate (paramagnetic) spin environments. This canonical problem has important connections to a number of physical systems, and is perfectly suited for experimental realization with ultracold atoms in an optical lattice. At the short-to-intermediate time scale that we can access using a stochastic-series-type numeric scheme, the propagation turns out to be distinctly nondiffusive with the probability distribution featuring minima in both space and time due to quantum interference, yet the motion is not ballistic, except at the beginning...
June 17, 2016: Physical Review Letters
Mantas Šimėnas, Sergejus Balčiūnas, Mirosław Ma Combining Cedilla Czka, Jūras Banys, Evaldas E Tornau
We propose a combined experimental and numerical study to describe an order-disorder structural phase transition in perovskite-based [(CH3)2NH2][M(HCOO)3] (M = Zn(2+), Mn(2+), Fe(2+), Co(2+) and Ni(2+)) dense metal-organic frameworks (MOFs). The three-fold degenerate orientation of the molecular (CH3)2NH2(+) (DMA(+)) cation implies a selection of the statistical three-state model of the Potts type. It is constructed on a simple cubic lattice where each lattice point can be occupied by a DMA(+) cation in one of the available states...
July 21, 2016: Physical Chemistry Chemical Physics: PCCP
Tadashi Orihara, Kazunari Hirota, Reiji Yokota, Daisuke Kunita, Yuji Itoh, Tosho Rii, Takashi Koto, Tomoyuki Hiraoka, Makoto Inoue, Akito Hirakata
PURPOSE: To evaluate clinical characteristics of rhegmatogenous retinal detachment in high myopic and phakic eyes. SUBJECTS AND METHOD: The subjects were 1174 eyes of phakic rhegmatogenous retinal detachment detected in 1199 eyes that underwent initial vitreoretinal surgery between April 2006 and March 2011. Eyes with macular hole retinal detachment or secondary retinal detachment were excluded. The 486 eyes with high myopia (spherical equivalent ≤ -6.0 D or axial length ≥ 26...
May 2016: Nippon Ganka Gakkai Zasshi
Hassan Chamati, Silvano Romano
In a previous paper [Phys. Rev. E 90, 022506 (2014)PLEEE81539-375510.1103/PhysRevE.90.022506], we studied the thermodynamic and structural properties of a three-dimensional simple-cubic lattice model with dipolarlike interaction, truncated at nearest-neighbor separation, for which the existence of an ordering transition at finite temperature had been proven mathematically; here we extend our investigation, addressing the full-ranged counterpart of the model, for which the critical behavior had been investigated theoretically and experimentally...
May 2016: Physical Review. E
Haifa A Madi, Richard J Haynes, Diana Depla, Morten D de la Cour, Sarit Lesnik-Oberstein, Mahi M K Muqit, Niall Patton, Nick Price, David H W Steel
PURPOSE: To describe the characteristics and outcomes of patients presenting with rhegmatogenous retinal detachment (RRD) after ocriplasmin (OCP) injection. METHODS: Retrospective, multi-centre, observational case series with case note review. RESULTS: Eight patients with symptomatic vitreomacular traction (six with concomitant macular hole) were diagnosed with RRD after a median of 16 days (range 3-131 days) post-OCP injection. Presentation was within 3 weeks of the OCP injection in six of the cases...
December 2016: Graefe's Archive for Clinical and Experimental Ophthalmology
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