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A Di Bernardo, O Millo, M Barbone, H Alpern, Y Kalcheim, U Sassi, A K Ott, D De Fazio, D Yoon, M Amado, A C Ferrari, J Linder, J W A Robinson
Electron pairing in the vast majority of superconductors follows the Bardeen-Cooper-Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG...
January 19, 2017: Nature Communications
H Chu, L Zhao, A de la Torre, T Hogan, S D Wilson, D Hsieh
Layered perovskite iridates realize a rare class of Mott insulators that are predicted to be strongly spin-orbit coupled analogues of the parent state of cuprate high-temperature superconductors. Recent discoveries of pseudogap, magnetic multipolar ordered and possible d-wave superconducting phases in doped Sr2IrO4 have reinforced this analogy among the single layer variants. However, unlike the bilayer cuprates, no electronic instabilities have been reported in the doped bilayer iridate Sr3Ir2O7. Here we show that Sr3Ir2O7 realizes a weak Mott state with no cuprate analogue by using ultrafast time-resolved optical reflectivity to uncover an intimate connection between its insulating gap and antiferromagnetism...
January 16, 2017: Nature Materials
Marcin M Wysokiński, Jan Kaczmarczyk
We investigate the effect of the electron-hole (e-h) symmetry breaking on d-wave superconductivity induced by non-local effects of correlations in the generalized Hubbard model. The symmetry breaking is introduced in a two-fold manner: by the next-to-nearest neighbor hopping of electrons and by the charge-bond interaction-the off-diagonal term of the Coulomb potential. Both terms lead to a pronounced asymmetry of the superconducting order parameter. The next-to-nearest neighbor hopping enhances superconductivity for h-doping, while diminishes it for e-doping...
January 16, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
R E Goetz, T A Isaev, B Nikoobakht, R Berger, C P Koch
Photoelectron circular dichroism refers to the forward/backward asymmetry in the photoelectron angular distribution with respect to the propagation axis of circularly polarized light. It has recently been demonstrated in femtosecond multi-photon photoionization experiments with randomly oriented camphor and fenchone molecules [C. Lux et al., Angew. Chem., Int. Ed. 51, 4755 (2012) and C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013)]. A theoretical framework describing this process as (2+1) resonantly enhanced multi-photon ionization is constructed, which consists of two-photon photoselection from randomly oriented molecules and successive one-photon ionization of the photoselected molecules...
January 14, 2017: Journal of Chemical Physics
Karl F Kothbauer
OBJECTIVE: To provide a summary of the intraoperative monitoring of muscle motor evoked potentials (MEPs) based on the presence-absence concept during neurosurgical operations along the spinal cord. METHOD: Expert review. DISCUSSION: The measurable parameters of MEPs, such as signal amplitudes and thresholds vary considerably both during a single surgery in a single individual patient as well as between individuals and operations. The presence or absence of responses irrespective of stimulus intensity and response amplitude is much more clearly defined...
January 2017: Journal of Clinical Neurophysiology: Official Publication of the American Electroencephalographic Society
David B MacDonald
Intraoperative motor evoked potentials include the D-wave as a surrogate for long-term motor outcome and muscle motor evoked potentials as a surrogate for early outcome. Their efficacy depends on excluding confounding factors and on warning criteria; insufficiently sensitive criteria could result in unpredicted deficits, whereas excessively sensitive ones could cause false alarms deterring surgical treatment and jading surgeons to alerts, eventually leading to deficits through failure to intervene. Although D-waves have few indications, they are nonsynaptic, linear, and stable-properties that support amplitude reduction criteria: >50% for intramedullary spinal cord tumor surgery and >30% to 40% for peri-Rolandic brain surgery...
January 2017: Journal of Clinical Neurophysiology: Official Publication of the American Electroencephalographic Society
M Gavaret, S Pesenti, M S Diop-Sene, E Choufani, G Bollini, J-L Jouve
BACKGROUND: In spinal deformity surgery, iatrogenic spinal cord injury is the most feared complication. Intraoperative monitoring (IOM) of the spinal cord assesses its functional integrity and allows significant reduction of the rate of spinal cord injury. HYPOTHESIS: In case of severe IOM alert, lesional level diagnosis constitutes supplementary and useful information. MATERIAL AND METHODS: This study was retrospective and monocentric. In our institution, 1062 pediatric spinal deformity surgeries have been monitored since 2004...
December 14, 2016: Orthopaedics & Traumatology, Surgery & Research: OTSR
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
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