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lattice degeneration

Bora Atalay, A Nihat Berker
Discrete-spin systems with maximally random nearest-neighbor interactions that can be symmetric or asymmetric, ferromagnetic or antiferromagnetic, including off-diagonal disorder, are studied, for the number of states q=3,4 in d dimensions. We use renormalization-group theory that is exact for hierarchical lattices and approximate (Migdal-Kadanoff) for hypercubic lattices. For all d>1 and all noninfinite temperatures, the system eventually renormalizes to a random single state, thus signaling q×q degenerate ordering...
May 2018: Physical Review. E
Yong-Lei Wang, Xiaoyu Ma, Jing Xu, Zhi-Li Xiao, Alexey Snezhko, Ralu Divan, Leonidas E Ocola, John E Pearson, Boldizsar Janko, Wai-Kwong Kwok
Geometric frustration emerges when local interaction energies in an ordered lattice structure cannot be simultaneously minimized, resulting in a large number of degenerate states. The numerous degenerate configurations may lead to practical applications in microelectronics 1 , such as data storage, memory and logic 2 . However, it is difficult to achieve very high degeneracy, especially in a two-dimensional system3,4 . Here, we showcase in situ controllable geometric frustration with high degeneracy in a two-dimensional flux-quantum system...
June 11, 2018: Nature Nanotechnology
O Thomas, C Lippe, T Eichert, H Ott
Feshbach resonances are a powerful tool to tune the interaction in an ultracold atomic gas. The commonly used magnetic Feshbach resonances are specific for each species and are restricted with respect to their temporal and spatial modulation. Optical Feshbach resonances are an alternative which can overcome this limitation. Here, we show that ultra-long-range Rydberg molecules can be used to implement an optical Feshbach resonance. Tuning the on-site interaction of a degenerate Bose gas in a 3D optical lattice, we demonstrate a similar performance compared to recent realizations of optical Feshbach resonances using intercombination transitions...
June 8, 2018: Nature Communications
Yuki Iguchi, Kazutoshi Inoue, Taiki Sugiyama, Hiroshi Yanagi
SnS is a promising photovoltaic semiconductor owing to its suitable band gap energy and high optical absorption coefficient for highly efficient thin film solar cells. The most significant carnage is demonstration of n-type SnS. In this study, Cl-doped n-type single crystals were grown using SnCl2 self-flux method. The obtained crystal was lamellar, with length and width of a few millimeters and thickness ranging between 28 and 39 μm. X-ray diffraction measurements revealed the single crystals had an orthorhombic unit cell...
June 5, 2018: Inorganic Chemistry
Yumiko Yonemoto, Seita Morishita, Masanori Fukumoto, Masashi Mimura, Takaki Sato, Teruyo Kida, Shota Kojima, Hidehiro Oku, Jun Sugasawa, Tsunehiko Ikeda
RATIONALE: The aim of this study was to report a case of Down syndrome (DS) complicated with bilateral retinal detachment (RD) due to unusual retinal degeneration. PATIENT CONCERNS: A 9-year-old girl complained of bilateral visual disturbance during a follow-up examination for myopia and strabismus. DIAGNOSES: Slit-lamp examination revealed moderate posterior subcapsular cataract in both eyes. B-mode echography showed bilateral bullous RD; however, it was difficult to detect the causal retinal breaks due to poor mydriasis...
June 2018: Medicine (Baltimore)
Solomon Owerre
We study the nontrivial linear magnon band crossings in the collinear antiferromagnets on the two-dimensional (2D) CaVO lattice, also realized in some iron-based superconductors such as AFe$_{1.6+x}$Se$_2$ (A = K, Rb, Cs). It is shown that the combination of space-inversion and time-reversal symmetry ($\mathcal{PT}$-symmetry) leads to doubly-degenerate eight magnon branches, which cross each other linearly along a one-dimensional loop in the 2D Brillouin zone. We show that the Dirac nodal loops (DNLs) are not present in the collinear ferromagnet on this lattice...
May 30, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Mingu Kang, Sung Won Jung, Woo Jong Shin, Yeongsup Sohn, Sae Hee Ryu, Timur K Kim, Moritz Hoesch, Keun Su Kim
Two-dimensional (2D) crystals have emerged as a class of materials with tunable carrier density 1 . Carrier doping to 2D semiconductors can be used to modulate many-body interactions 2 and to explore novel composite particles. The Holstein polaron is a small composite particle of an electron that carries a cloud of self-induced lattice deformation (or phonons)3-5 , which has been proposed to play a key role in high-temperature superconductivity 6 and carrier mobility in devices 7 . Here we report the discovery of Holstein polarons in a surface-doped layered semiconductor, MoS2 , in which a puzzling 2D superconducting dome with the critical temperature of 12 K was found recently8-11 ...
May 28, 2018: Nature Materials
Tyler J Slade, Jann A Grovogui, Shiqiang Hao, Trevor P Bailey, Runchu Ma, Xia Hua, Aurélie Guéguen, Ctirad Uher, Chris Wolverton, Vinayak P Dravid, Mercouri G Kanatzidis
Thermoelectric devices directly convert heat into electrical energy and are highly desired for emerging applications in waste heat recovery. Currently, PbTe based compounds are the leading thermoelectric materials in the intermediate temperature regime (∼800 K); however, integration into commercial devices has been limited. This is largely because the performance of PbTe, which is maximized ∼900 K, is too low over the temperatures of interest for most potential commercial applications (generally under 600 K)...
May 25, 2018: Journal of the American Chemical Society
Adarsh S Patri, Kyusung Hwang, Hyun-Woo Lee, Yong Baek Kim
We theoretically investigate the mechanism to generate large intrinsic spin Hall effect in iridates or more broadly in 5d transition metal oxides with strong spin-orbit coupling. We demonstrate such a possibility by taking the example of orthorhombic perovskite iridate with nonsymmorphic lattice symmetry, SrIrO3 , which is a three-dimensional semimetal with nodal line spectrum. It is shown that large intrinsic spin Hall effect arises in this system via the spin-Berry curvature originating from the nearly degenerate electronic spectra surrounding the nodal line...
May 23, 2018: Scientific Reports
Kunyong Xu, Eric K Chin, Steven R Bennett, David F Williams, Edwin H Ryan, Sundeep Dev, Robert A Mittra, Polly A Quiram, John B Davies, David Wilkin Parke, Herbert Culver Boldt, David R P Almeida
PURPOSE: To determine predictive factors of proliferative vitreoretinopathy (PVR) formation after uncomplicated primary retinal detachment repair. METHODS: Retrospective, single-center, case-control study of 74 consecutive patients with (37 eyes) and without (37 eyes) PVR formation after undergoing uncomplicated primary surgery for retinal detachment repair. Logistic regression was used to assess factors associated with PVR formation. RESULTS: Retinal detachment involving the macula was 4...
May 21, 2018: Retina
Jesús Daniel Valenzuela-Sau, Raúl García-Llamas
We calculated the out-of-plane band structure of a two-dimensional dispersive photonic crystal (PC). To achieve this goal, the plane wave expansion method was implemented in conjunction with a numerical algorithm, the dispersive photonic crystal iterative method. The PC is an array of circular cross-sectional dispersive MgO Lorentz single-pole rods in a square lattice. The frequency bands are calculated starting at Γ as a function of the oblique component of the wave vector. For the lowest frequencies, it was found that the modes bend drastically to the horizon as the dielectric constant ϵ(ω) is increased to a very positive value...
May 15, 2018: Optics Letters
B Chakraborty, C T H Davies, C DeTar, A X El-Khadra, E Gámiz, Steven Gottlieb, D Hatton, J Koponen, A S Kronfeld, J Laiho, G P Lepage, Yuzhi Liu, P B Mackenzie, C McNeile, E T Neil, J N Simone, R Sugar, D Toussaint, R S Van de Water, A Vaquero
All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon's anomalous magnetic moment to date have been performed with degenerate up- and down-quark masses. Here we calculate directly the strong-isospin-breaking correction to a_{μ}^{HVP} for the first time with physical values of m_{u} and m_{d} and dynamical u, d, s, and c quarks, thereby removing this important source of systematic uncertainty. We obtain a relative shift to be applied to lattice-QCD results obtained with degenerate light-quark masses of δa_{μ}^{HVP,m_{u}≠m_{d}}=+1...
April 13, 2018: Physical Review Letters
Luiz Antonio Ribeiro, Fábio Ferreira Monteiro, Wiliam Ferreira da Cunha, Geraldo Magela E Silva
The dynamical scattering of two oppositely charged bipolarons in non-degenerate organic semiconducting lattices is numerically investigated in the framework of a one-dimensional tight-biding-Hubbard model that includes lattice relaxation. Our findings show that it is possible for the bipolaron pair to merge into a state composed of a confined soliton-antisoliton pair, which is characterized by the appearance of states within less than 0.1 eV from the Fermi level. This compound is in a narrow analogy to a meson confining a quark-antiquark pair...
April 26, 2018: Scientific Reports
Farokh Mivehvar, Stefan Ostermann, Francesco Piazza, Helmut Ritsch
Supersolids are characterized by the counterintuitive coexistence of superfluid and crystalline order. Here we study a supersolid phase emerging in the steady state of a driven-dissipative system. We consider a transversely pumped Bose-Einstein condensate trapped along the axis of a ring cavity and coherently coupled to a pair of degenerate counterpropagating cavity modes. Above a threshold pump strength the interference of photons scattered into the two cavity modes results in an emergent superradiant lattice, which spontaneously breaks the continuous translational symmetry towards a periodic atomic pattern...
March 23, 2018: Physical Review Letters
Yujeong Lee, Kang Lib Kim, Han Sol Kang, Beomjin Jeong, Chanho Park, Insung Bae, Seok Ju Kang, Youn Jung Park, Cheolmin Park
Epitaxial crystallization of thin poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) films is important for the full utilization of their ferroelectric properties. Epitaxy can offer a route for maximizing the degree of crystallinity with the effective orientation of the crystals with respect to the electric field. Despite various approaches for the epitaxial control of the crystalline structure of PVDF-TrFE, its epitaxy on a semiconductor is yet to be accomplished. Herein, the epitaxial growth of PVDF-TrFE crystals on a single-crystalline organic semiconductor rubrene grown via physical vapor deposition is presented...
May 2018: Small
San-Dong Guo, Peng Chen
Topological semimetals are currently attracting increasing interest due to their potential applications in topological qubits and low-power electronics, which are closely related to their thermal transport properties. Recently, the triply degenerate nodal points near the Fermi level of WC are observed by using angle-resolved photoemission spectroscopy. In this work, by solving the Boltzmann transport equation based on first-principles calculations, we systematically investigate the phonon transport properties of topological semimetals WC and WN...
April 14, 2018: Journal of Chemical Physics
Franck Pichaud
The fly photoreceptor has long been used as a model to study sensory neuron morphogenesis and retinal degeneration. In particular, elucidating how these cells are built continues to help further our understanding of the mechanisms of polarized cell morphogenesis, intracellular trafficking and the causes of human retinal pathologies. The conserved PAR complex, which in flies consists of Cdc42-PAR6-aPKC-Bazooka, and the transmembrane protein Crumbs (Crb) are key players during photoreceptor morphogenesis. While the PAR complex regulates polarity in many cell types, Crb function in polarity is relatively specific to epithelial cells...
2018: Frontiers in Cellular Neuroscience
Guangqian Ding, Cong Wang, Guoying Gao, Kailun Yao, Chaochao Dun, Chunbao Feng, Dengfeng Li, Gang Zhang
High band degeneracy and glassy phonon transport are two remarkable features of highly efficient thermoelectric (TE) materials. The former promotes the power factor, while the latter aims to break the lower limit of lattice thermal conductivity through phonon scattering. Herein, we use the unique possibility offered by a two-dimensional superlattice-monolayer structure (SLM) to engineer the band degeneracy, charge density and phonon spectrum to maximize the thermoelectric figure of merit (ZT). First-principles calculations with Boltzmann transport equations reveal that the conduction bands of ZrSe2/HfSe2 SLM possess a highly degenerate level which gives a high n-type power factor; at the same time, the stair-like density of states yields a high Seebeck coefficient...
April 19, 2018: Nanoscale
David Z Chen, Victor Koh, Marcus Tan, Colin S Tan, Gerard Nah, Liang Shen, Mayuri Bhargava, Ching-Yu Cheng, Paul Zhao, Tien Yin Wong, Seang-Mei Saw
PURPOSE: To determine the type and prevalence of peripheral retinal changes and its relationship with axial length (AL) in a population of young Asian adult males. METHODS: This was a cross-sectional study of male subjects aged between 19 and 25 years old. High myopes [spherical equivalent refraction, (SER) < -6.00 D] were recruited and underwent further ocular investigations including dilated retinal photography and binocular indirect ophthalmoscopy by two trained ophthalmologists...
March 25, 2018: Acta Ophthalmologica
G Edward Marti, Ross B Hutson, Akihisa Goban, Sara L Campbell, Nicola Poli, Jun Ye
We implement imaging spectroscopy of the optical clock transition of lattice-trapped degenerate fermionic Sr in the Mott-insulating regime, combining micron spatial resolution with submillihertz spectral precision. We use these tools to demonstrate atomic coherence for up to 15 s on the clock transition and reach a record frequency precision of 2.5×10^{-19}. We perform the most rapid evaluation of trapping light shifts and record a 150 mHz linewidth, the narrowest Rabi line shape observed on a coherent optical transition...
March 9, 2018: Physical Review Letters
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