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Jian Kang, Rafael M Fernandes
The origin of the high-temperature superconducting state observed in FeSe thin films, whose phase diagram displays no sign of magnetic order, remains a hotly debated topic. Here we investigate whether fluctuations arising due to the proximity to a nematic phase, which is observed in the phase diagram of this material, can promote superconductivity. We find that nematic fluctuations alone promote a highly degenerate pairing state, in which both s-wave and d-wave symmetries are equally favored, and T_{c} is consequently suppressed...
November 18, 2016: Physical Review Letters
N Chancellor, S Zohren, P A Warburton, S C Benjamin, S Roberts
We demonstrate a direct mapping of max k-SAT problems (and weighted max k-SAT) to a Chimera graph, which is the non-planar hardware graph of the devices built by D-Wave Systems Inc. We further show that this mapping can be used to map a similar class of maximum satisfiability problems where the clauses are replaced by parity checks over potentially large numbers of bits. The latter is of specific interest for applications in decoding for communication. We discuss an example in which the decoding of a turbo code, which has been demonstrated to perform near the Shannon limit, can be mapped to a Chimera graph...
November 18, 2016: Scientific Reports
Goichi Akiyama, Celso Soiti Matsumoto, Kei Shinoda, Gaku Terauchi, Harue Matsumoto, Emiko Watanabe, Takeshi Iwata, Atsushi Mizota, Yozo Miyake
Scleral indentation is widely used to examine the peripheral fundus, however it can increase the intraocular pressure (IOP) to high levels which can then affect retinal function. We evaluated the effects of scleral indentation on the macular function electrophysiologically. Intraoperative focal macular electroretinograms (iFMERGs) were recorded with and without controlling the IOP in 7 eyes. Without IOP control, the IOP increased from 21.7 ± 4.9 to 92.7 ± 20.2 mmHg significantly (P = 0.020) and the amplitudes of the b-wave (from 6...
October 20, 2016: Scientific Reports
Rong Yu, Andriy H Nevidomskyy
We study the symmetry and strength of the superconducting pairing in a two-orbital [Formula: see text] model for iron pnictides using the slave boson strong coupling approach. We show that the nearest-neighbor biquadratic interaction [Formula: see text] strongly affects the superconducting pairing phase diagram by promoting the [Formula: see text] B 1g and the [Formula: see text] A 1g channels. The resulting phase diagram consists of several competing pairing channels, including the isotropic [Formula: see text] A 1g channel, an anisotropic [Formula: see text] B 1g channel, and two [Formula: see text] pairing channels...
October 13, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Y A Kharkov, O P Sushkov
We find unknown s- and d-wave amplitudes of the recently discovered charge density wave (CDW) in underdoped cuprates. To do so we perform a combined analysis of experimental data for ortho-II YBa2Cu3Oy. The analysis includes data on nuclear magnetic resonance, resonant inelastic X-ray scattering, and hard X-ray diffraction. The amplitude of doping modulation found in our analysis is 3.5 · 10(-3) in a low magnetic field and T = 60 K, the amplitude is 6.5 · 10(-3) in a magnetic field of 30T and T = 1...
October 10, 2016: Scientific Reports
Kyuil Cho, Marcin Kończykowski, Serafim Teknowijoyo, Makariy A Tanatar, Yong Liu, Thomas A Lograsso, Warren E Straszheim, Vivek Mishra, Saurabh Maiti, Peter J Hirschfeld, Ruslan Prozorov
The mechanism of unconventional superconductivity in iron-based superconductors (IBSs) is one of the most intriguing questions in current materials research. Among non-oxide IBSs, (Ba1-x K x )Fe2As2 has been intensively studied because of its high superconducting transition temperature and fascinating evolution of the superconducting gap structure from being fully isotropic at optimal doping (x ≈ 0.4) to becoming nodal at x > 0.8. Although this marked evolution was identified in several independent experiments, there are no details of the gap evolution to date because of the lack of high-quality single crystals covering the entire K-doping range of the superconducting dome...
September 2016: Science Advances
Noriko Inoue, Hideshi Kawakami, Hideya Yamamoto, Chikako Ito, Saeko Fujiwara, Hideo Sasaki, Yasuki Kihara
The second derivative of the digital photoplethysmogram (SDPTG) is an indicator of arterial stiffness. The ratio of the height of the d wave to the a wave of the SDPTG (d/a) is associated with functional peripheral vascular tension and represents aortic-blood pressure (BP) augmented by reflection waves from the periphery. This longitudinal study aimed to investigate the relationship between SDPTG and cardiovascular mortality in middle-aged and elderly Japanese women. From 1998 to 2008, we recruited 4373 women (50-79 years old at baseline) who underwent medical check-ups and SDPTG measurement...
September 29, 2016: Hypertension Research: Official Journal of the Japanese Society of Hypertension
Yudong Cao, Shuxian Jiang, Debbie Perouli, Sabre Kais
Here we consider using quantum annealing to solve Set Cover with Pairs (SCP), an NP-hard combinatorial optimization problem that plays an important role in networking, computational biology, and biochemistry. We show an explicit construction of Ising Hamiltonians whose ground states encode the solution of SCP instances. We numerically simulate the time-dependent Schrödinger equation in order to test the performance of quantum annealing for random instances and compare with that of simulated annealing. We also discuss explicit embedding strategies for realizing our Hamiltonian construction on the D-wave type restricted Ising Hamiltonian based on Chimera graphs...
September 27, 2016: Scientific Reports
Y Zhang, J J Lee, R G Moore, W Li, M Yi, M Hashimoto, D H Lu, T P Devereaux, D-H Lee, Z-X Shen
Superconductivity originates from pairing of electrons near the Fermi energy. The Fermi surface topology and pairing symmetry are thus two pivotal characteristics of a superconductor. Superconductivity in one monolayer (1 ML) FeSe thin film has attracted great interest recently due to its intriguing interfacial properties and possibly high superconducting transition temperature over 65 K. Here, we report high-resolution measurements of the Fermi surface and superconducting gaps in 1 ML FeSe using angle-resolved photoemission spectroscopy...
September 9, 2016: Physical Review Letters
Yoni Schattner, Max H Gerlach, Simon Trebst, Erez Berg
We study the onset of spin-density wave order in itinerant electron systems via a two-dimensional lattice model amenable to numerically exact, sign-problem-free determinantal quantum Monte Carlo simulations. The finite-temperature phase diagram of the model reveals a dome-shaped d-wave superconducting phase near the magnetic quantum phase transition. Above the critical superconducting temperature, an extended fluctuation regime manifests itself in the opening of a gap in the electronic density of states and an enhanced diamagnetic response...
August 26, 2016: Physical Review Letters
T Ekino, A M Gabovich, Mai Suan Li, H Szymczak, A I Voitenko
The quasiparticle tunnel current J(V) between the superconducting ab-planes along the c-axis and the corresponding conductance [Formula: see text] were calculated for symmetric junctions composed of disordered d-wave layered superconductors partially gapped by charge density waves (CDWs). Here, V is the voltage. Both the checkerboard and unidirectional CDWs were considered. It was shown that the spatial spread of the CDW-pairing strength substantially smears the peculiarities of G(V) appropriate to uniform superconductors...
November 9, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Tinghai Cheng, Xiaohui Lu, Hongwei Zhao, Dong Chen, Pu He, Liang Wang, Xilu Zhao
The smooth impact drive mechanism (SIDM) actuator is traditionally excited by a saw-tooth wave, but it requires large input voltages for high-speed operation and load capacity. To improve the output characteristic of the SIDM operating at low input voltage, a novel driving method based on ultrasonic friction reduction technology is proposed in this paper. A micro-amplitude sinusoidal signal with high frequency is applied to the rapid deformation stage of the traditional saw-tooth wave. The proposed driving method can be realized by a composite waveform that includes a driving wave (D-wave) and a friction regulation wave (FR-wave)...
August 2016: Review of Scientific Instruments
Dale A Burkett, Cameron Slorach, Sonali S Patel, Andrew N Redington, D Dunbar Ivy, Luc Mertens, Adel K Younoszai, Mark K Friedberg
BACKGROUND: Through ventricular interdependence, pulmonary hypertension (PH) induces left ventricular (LV) dysfunction. We hypothesized that pediatric PH patients have LV diastolic dysfunction, related to adverse pulmonary hemodynamics, leftward septal shift, and prolonged right ventricular systole. METHODS AND RESULTS: Echocardiography was prospectively performed at 2 institutions in 54 pediatric PH patients during cardiac catheterization and in 54 matched controls...
September 2016: Circulation. Cardiovascular Imaging
Wang Yang, Yi Li, Congjun Wu
We systematically generalize the exotic ^{3}He-B phase, which not only exhibits unconventional symmetry but is also isotropic and topologically nontrivial, to arbitrary partial-wave channels with multicomponent fermions. The concrete example with four-component fermions is illustrated including the isotropic f-, p-, and d-wave pairings in the spin septet, triplet, and quintet channels, respectively. The odd partial-wave channel pairings are topologically nontrivial, while pairings in even partial-wave channels are topologically trivial...
August 12, 2016: Physical Review Letters
Jae-Hwan Kim, So-Young Kim, Ki-Dong Eom
This study was performed to identify the relationship between the hepatic vein (HV) measurements, including flow velocity and waveform, performed with pulsed-wave (PW) Doppler ultrasonography and severity of tricuspid regurgitation (TR) in dogs. The study included 22 dogs with TR and 7 healthy dogs. The TR group was subdivided into 3 groups according to the TR jet profile in echocardiographic examination. The hepatic venous waveform was obtained and classified into 3 types. The measurements of HV, including the maximal velocities of the atrial systolic (A), systolic (S), end ventricular systolic (V), and diastolic (D) waves and the ratio of the S- and D- wave velocities (S:D ratio), were acquired...
August 10, 2016: Journal of Veterinary Science
Daniel Gomez-Cardona, Juan Pablo Cruz-Bastida, Ke Li, Adam Budde, Jiang Hsieh, Guang-Hong Chen
PURPOSE: Noise characteristics of clinical multidetector CT (MDCT) systems can be quantified by the noise power spectrum (NPS). Although the NPS of CT has been extensively studied in the past few decades, the joint impact of the bowtie filter and object position on the NPS has not been systematically investigated. This work studies the interplay of these two factors on the two dimensional (2D) local NPS of a clinical CT system that uses the filtered backprojection algorithm for image reconstruction...
August 2016: Medical Physics
Pierre Massat, Donato Farina, Indranil Paul, Sandra Karlsson, Pierre Strobel, Pierre Toulemonde, Marie-Aude Méasson, Maximilien Cazayous, Alain Sacuto, Shigeru Kasahara, Takasada Shibauchi, Yuji Matsuda, Yann Gallais
The spontaneous appearance of nematicity, a state of matter that breaks rotation but not translation symmetry, is one of the most intriguing properties of the iron-based superconductors (Fe SC), and has relevance for the cuprates as well. Establishing the critical electronic modes behind nematicity remains a challenge, however, because their associated susceptibilities are not easily accessible by conventional probes. Here, using FeSe as a model system, and symmetry-resolved electronic Raman scattering as a probe, we unravel the presence of critical charge nematic fluctuations near the structural/nematic transition temperature, [Formula: see text] 90 K...
August 16, 2016: Proceedings of the National Academy of Sciences of the United States of America
J P Rodriguez
We obtain the exact low-energy spectrum of two mobile holes in a t-J model for an isolated layer in an iron-pnictide superconductor. The minimum d xz and d yz orbitals per iron atom are included, with no hybridization between the two. After tuning the Hund coupling to a putative quantum critical point (QCP) that separates a commensurate spin-density wave from a hidden-order antiferromagnet at half filling, we find an s-wave hole-pair groundstate and a d-wave hole-pair excited state. Near the QCP, both alternate in sign between hole Fermi surface pockets at the Brillouin zone center and emergent electron Fermi surface pockets at momenta that correspond to commensurate spin-density waves (cSDW)...
September 21, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Chandra M Varma
The anomalous transport and thermodynamic properties in the quantum-critical region, in the cuprates, and in the quasi-two dimensional Fe-based superconductors and heavy-fermion compounds, have the same temperature dependences. This can occur only if, despite their vast microscopic differences, a common statistical mechanical model describes their phase transitions. The antiferromagnetic (AFM)-ic models for the latter two, just as the loop-current model for the cuprates, map to the dissipative XY model. The solution of this model in (2+1)D reveals that the critical fluctuations are determined by topological excitations, vortices and a variety of instantons, and not by renormalized spin-wave theories of the Landau-Ginzburg-Wilson type, adapted by Moriya, Hertz and others for quantum-criticality...
August 2016: Reports on Progress in Physics
Qisi Wang, J T Park, Yu Feng, Yao Shen, Yiqing Hao, Bingying Pan, J W Lynn, A Ivanov, Songxue Chi, M Matsuda, Huibo Cao, R J Birgeneau, D V Efremov, Jun Zhao
An essential step toward elucidating the mechanism of superconductivity is to determine the sign or phase of the superconducting order parameter, as it is closely related to the pairing interaction. In conventional superconductors, the electron-phonon interaction induces attraction between electrons near the Fermi energy and results in a sign-preserved s-wave pairing. For high-temperature superconductors, including cuprates and iron-based superconductors, prevalent weak coupling theories suggest that the electron pairing is mediated by spin fluctuations which lead to repulsive interactions, and therefore that a sign-reversed pairing with an s_{±} or d-wave symmetry is favored...
May 13, 2016: Physical Review Letters
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