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Unurbat Erdenemunkh, Brian Koopman, Ling Fu, Kamalesh Chatterjee, W D Wise, G D Gu, E W Hudson, Michael C Boyer
We use scanning tunneling microscopy (STM) to study magnetic Fe impurities intentionally doped into the high-temperature superconductor Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}. Our spectroscopic measurements reveal that Fe impurities introduce low-lying resonances in the density of states at Ω_{1}≈4  meV and Ω_{2}≈15  meV, allowing us to determine that, despite having a large magnetic moment, potential scattering of quasiparticles by Fe impurities dominates magnetic scattering. In addition, using high-resolution spatial characterizations of the local density of states near and away from Fe impurities, we detail the spatial extent of impurity-affected regions as well as provide a local view of impurity-induced effects on the superconducting and pseudogap states...
December 16, 2016: Physical Review Letters
Ana Lidia Arellano Ortiz, Florinda Jiménez Vega, Cecilia Díaz Hernández, Muricio Salcedo Vargas, Antonio De la Mora Covarrubias, José Alberto López Díaz, Claudia Lucía Vargas Requena, María Lorena Cassís Nosthas
Introducción: las lesiones intraepiteliales escamosas (LIE) son un estado de transición hacia el cáncer cervicouterino (CaCu) y un déficit de micronutrientes puede acelerar este proceso. Por ello, determinar la existencia de este déficit y conocer qué factores se asocian permitiría una posible prevención en esta población de riesgo.Objetivo: determinar la presencia de alguna deficiencia de micronutrientes involucrados en el proceso anticancerígeno y asociar este déficit con hábitos y factores demográficos en pacientes con LIE de Ciudad Juárez, Chihuahua, México...
July 19, 2016: Nutrición Hospitalaria: Organo Oficial de la Sociedad Española de Nutrición Parenteral y Enteral
R M Keumo Tsiaze, A V Wirngo, S E Mkam Tchouobiap, A J Fotue, E Baloïtcha, M N Hounkonnou
We report on a study of the superconducting order parameter thermodynamic fluctuations in YBa_{2}Cu_{3}O_{7-δ},Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}, and KOs_{2}O_{6} compounds. A nonperturbative technique within the framework of the renormalized Gaussian approach is proposed. The essential features are reported (analytically and numerically) through Ginzburg-Landau (GL) model-based calculations which take into account both the dimension and the microscopic parameters of the system. By presenting a self-consistent approach improvement on the GL theory, a technique for obtaining corrections to the asymptotic critical behavior in terms of nonuniversal parameters is developed...
June 2016: Physical Review. E
Th Jacobs, Y Simsek, Y Koval, P Müller, V M Krasnov
Our recently discovered electrical doping technique allows a broad-range variation of carrier concentration without changing the chemical composition. We show that it is possible to induce superconductivity in a nondoped insulating sample and to tune it reversibly all the way to an overdoped metallic state. This way, we can investigate the whole doping diagram of one and the same sample. Our study reveals two distinct critical points. The one at the overdoped side is associated with the onset of the pseudogap and with the metal-to-insulator transition in the c-axis transport...
February 12, 2016: Physical Review Letters
Yan-Feng Lv, Wen-Lin Wang, Jun-Ping Peng, Hao Ding, Yang Wang, Lili Wang, Ke He, Shuai-Hua Ji, Ruidan Zhong, John Schneeloch, Gen-Da Gu, Can-Li Song, Xu-Cun Ma, Qi-Kun Xue
Understanding the mechanism of high transition temperature (T{c}) superconductivity in cuprates has been hindered by the apparent complexity of their multilayered crystal structure. Using a cryogenic scanning tunneling microscopy (STM), we report on layer-by-layer probing of the electronic structures of all ingredient planes (BiO, SrO, CuO{2}) of Bi{2}Sr{2}CaCu_2}O{8+δ} superconductor prepared by argon-ion bombardment and annealing technique. We show that the well-known pseudogap (PG) feature observed by STM is inherently a property of the BiO planes and thus irrelevant directly to Cooper pairing...
December 4, 2015: Physical Review Letters
Jian-Bo Zhang, Viktor V Struzhkin, Wenge Yang, Ho-Kwang Mao, Hai-Qing Lin, Yong-Chang Ma, Nan-Lin Wang, Xiao-Jia Chen
The systematic evolution of the structural, vibrational, and superconducting properties of nearly optimally doped Tl2Ba2CaCu2O(8+δ) with pressure up to 30 GPa is studied by x-ray diffraction, Raman scattering, and magnetic susceptibility measurements. No phase transformation is observed in the studied pressure regime. The obtained lattice parameters and unit-cell volume continuously decrease with pressure by following the expected equation of state. The axial ratio of c/a exhibits an anomaly starting from 9 GPa...
November 11, 2015: Journal of Physics. Condensed Matter: An Institute of Physics Journal
M I Dolz, Y Fasano, N R Cejas Bolecek, H Pastoriza, V Mosser, M Li, M Konczykowski
We detect the persistence of the solidification and order-disorder first-order transition lines in the phase diagram of nanocrystalline Bi_{2}Sr_{2}CaCu_{2}O_{8} vortex matter down to a system size of less than one hundred vortices. The temperature location of the vortex solidification transition line is not altered by decreasing the sample size although there is a depletion of the entropy jump at the transition with respect to macroscopic vortex matter. The solid order-disorder phase transition field moves upward on decreasing the system size due to the increase of the surface-to-volume ratio of vortices entailing a decrease on the average vortex binding energy...
September 25, 2015: Physical Review Letters
A Kreisel, Peayush Choubey, T Berlijn, W Ku, B M Andersen, P J Hirschfeld
We apply a recently developed method combining first principles based Wannier functions with solutions to the Bogoliubov-de Gennes equations to the problem of interpreting STM data in cuprate superconductors. We show that the observed images of Zn on the surface of Bi_{2}Sr_{2}CaCu_{2}O_{8} can only be understood by accounting for the tails of the Cu Wannier functions, which include significant weight on apical O sites in neighboring unit cells. This calculation thus puts earlier crude "filter" theories on a microscopic foundation and solves a long-standing puzzle...
May 29, 2015: Physical Review Letters
S Benhabib, A Sacuto, M Civelli, I Paul, M Cazayous, Y Gallais, M-A Méasson, R D Zhong, J Schneeloch, G D Gu, D Colson, A Forget
We report a fine tuned doping study of strongly overdoped Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} single crystals using electronic Raman scattering. Combined with theoretical calculations, we show that the doping, at which the normal-state pseudogap closes, coincides with a Lifshitz quantum phase transition where the active holelike Fermi surface becomes electronlike. This conclusion suggests that the microscopic cause of the pseudogap is sensitive to the Fermi surface topology. Furthermore, we find that the superconducting transition temperature is unaffected by this transition, demonstrating that their origins are different on the overdoped side...
April 10, 2015: Physical Review Letters
Valentina Bisogni, Krzysztof Wohlfeld, Satoshi Nishimoto, Claude Monney, Jan Trinckauf, Kejin Zhou, Roberto Kraus, Klaus Koepernik, Chinnathambi Sekar, Vladimir Strocov, Bernd Büchner, Thorsten Schmitt, Jeroen van den Brink, Jochen Geck
Fractionalization of an electronic quasiparticle into spin, charge, and orbital parts is a fundamental and characteristic property of interacting electrons in one dimension. However, real materials are never strictly one dimensional and the fractionalization phenomena are hard to observe. Here we studied the spin and orbital excitations of the anisotropic ladder material CaCu_{2}O_{3}, whose electronic structure is not one dimensional. Combining high-resolution resonant inelastic x-ray scattering experiments with theoretical model calculations, we show that (i) spin-orbital fractionalization occurs in CaCu_{2}O_{3} along the leg direction x through the xz orbital channel as in a 1D system, and (ii) no fractionalization is observed for the xy orbital, which extends in both leg and rung direction, contrary to a 1D system...
March 6, 2015: Physical Review Letters
S Ooi, T Mochiku, M Tachiki, K Hirata
The vortex-lattice melting transition of a limited number of vortices confined in mesoscopic square superconductors was studied by c-axis resistance measurements using stacks of intrinsic Josephson junctions in Bi_{2}Sr_{2}CaCu_{2}O_{8+y}. In contrast to the melting transition in bulk crystals, we have first found a clear oscillatory behavior in the field dependence of the melting temperature in small samples of 5-10  μm square. The periods of the oscillations roughly obey the regularity of the matching conditions of square vortex lattices surrounded by a square boundary and the melting temperatures are enhanced around the vortex number of i^{2} (where i is an integer)...
February 27, 2015: Physical Review Letters
L Perfetti, B Sciolla, G Biroli, C J van der Beek, C Piovera, M Wolf, T Kampfrath
Despite extensive work on high-temperature superconductors, the critical behavior of an incipient condensate has so far been studied exclusively under equilibrium conditions. Here, we excite Bi(2)Sr(2)CaCu(2)O(8+δ) with a femtosecond laser pulse and monitor the subsequent nonequilibrium dynamics of the midinfrared conductivity. Our data allow us to discriminate temperature regimes where superconductivity is either coherent, fluctuating or vanishingly small. Above the transition temperature T(c), we make the striking observation that the relaxation to equilibrium exhibits power-law dynamics and scaling behavior, both for optimally and underdoped superconductors...
February 13, 2015: Physical Review Letters
F Kametani, J Jiang, M Matras, D Abraimov, E E Hellstrom, D C Larbalestier
Why Bi(2)Sr(2)CaCu(2)Ox (Bi2212) allows high critical current density Jc in round wires rather than only in the anisotropic tape form demanded by all other high temperature superconductors is important for future magnet applications. Here we compare the local texture of state-of-the-art Bi2212 and Bi2223 ((Bi,Pb)(2)Sr(2)Ca(2)Cu(3)O(10)), finding that round wire Bi2212 generates a dominant a-axis growth texture that also enforces a local biaxial texture (FWHM <15°) while simultaneously allowing the c-axes of its polycrystals to rotate azimuthally along and about the filament axis so as to generate macroscopically isotropic behavior...
2015: Scientific Reports
M Guarise, B Dalla Piazza, H Berger, E Giannini, T Schmitt, H M Rønnow, G A Sawatzky, J van den Brink, D Altenfeld, I Eremin, M Grioni
The high-Tc cuprate superconductors are close to antiferromagnetic order. Recent measurements of magnetic excitations have reported an intriguing similarity to the spin waves--magnons--of the antiferromagnetic insulating parent compounds, suggesting that magnons may survive in damped, broadened form throughout the phase diagram. Here we show by resonant inelastic X-ray scattering on Bi(2)Sr(2)CaCu(2)O(8+δ) (Bi-2212) that the analogy with spin waves is only partial. The magnon-like features collapse along the nodal direction in momentum space and exhibit a photon energy dependence markedly different from the Mott-insulating case...
2014: Nature Communications
D Meyers, S Middey, J-G Cheng, Swarnakamal Mukherjee, B A Gray, Yanwei Cao, J-S Zhou, J B Goodenough, Yongseong Choi, D Haskel, J W Freeland, T Saha-Dasgupta, J Chakhalian
With current research efforts shifting towards the 4d and 5d transition metal oxides, understanding the evolution of the electronic and magnetic structure as one moves away from 3d materials is of critical importance. Here we perform X-ray spectroscopy and electronic structure calculations on A-site-ordered perovskites with Cu in the A-site and the B-sites descending along the ninth group of the periodic table to elucidate the emerging properties as d-orbitals change from partially filled 3d to 4d to 5d. The results show that when descending from Co to Ir, the charge transfers from the cuprate-like Zhang-Rice state on Cu to the t(2g) orbital of the B site...
2014: Nature Communications
Ilija Zeljkovic, Jouko Nieminen, Dennis Huang, Tay-Rong Chang, Yang He, Horng-Tay Jeng, Zhijun Xu, Jinsheng Wen, Genda Gu, Hsin Lin, Robert S Markiewicz, Arun Bansil, Jennifer E Hoffman
The highest-temperature superconductors are electronically inhomogeneous at the nanoscale, suggesting the existence of a local variable that could be harnessed to enhance the superconducting pairing. Here we report the relationship between local doping and local strain in the cuprate superconductor Bi(2)Sr(2)CaCu(2)O(8+x). We use scanning tunneling microscopy to discover that the crucial oxygen dopants are periodically distributed in correlation with local strain. Our picoscale investigation of the intraunit-cell positions of all oxygen dopants provides essential structural input for a complete microscopic theory...
December 10, 2014: Nano Letters
Elisa Neves Vianna, Andrey José de Andrade, Fernando Braga Stehling Dias, Liléia Diotaiuti
INTRODUCTION: Rhodnius neglectus is a triatomine that colonizes different palm species. In this study, we aimed to describe the presence of this triatomine bug in the royal palms (Roystonea oleracea) in a rural region of the State of Goiás. METHODS: Palm infestation was investigated by dissecting the palms or by using live-bait traps. RESULTS: Two palm trees were infested by R. neglectus negative for Trypanosoma cruzi, the etiological agent for Chagas disease...
September 2014: Revista da Sociedade Brasileira de Medicina Tropical
M P M Dean, A J A James, R S Springell, X Liu, C Monney, K J Zhou, R M Konik, J S Wen, Z J Xu, G D Gu, V N Strocov, T Schmitt, J P Hill
We investigate the high-energy magnetic excitation spectrum of the high-T(c) cuprate superconductor Bi(2)Sr(2)CaCu(2)O(8+δ) (Bi-2212) using Cu L(3) edge resonant inelastic x-ray scattering. Broad, dispersive magnetic excitations are observed, with a zone boundary energy of ∼ 300 meV and a weak dependence on doping. These excitations are strikingly similar to the bosons proposed to explain the high-energy "kink" observed in photoemission. A phenomenological calculation of the spin response, based on a parametrization of the the angle-resolved photoemission spectroscopy derived electronic structure and Yang-Rice-Zhang quasiparticles, provides a reasonable prediction of the energy dispersion of the observed magnetic excitations...
April 5, 2013: Physical Review Letters
T Yilmaz, I Pletikosić, A P Weber, J T Sadowski, G D Gu, A N Caruso, B Sinkovic, T Valla
Proximity-induced superconductivity in a 3D topological insulator represents a new avenue for observing zero-energy Majorana fermions inside vortex cores. Relatively small gaps and low transition temperatures of conventional s-wave superconductors put hard constraints on these experiments. Significantly larger gaps and higher transition temperatures in cuprate superconductors might be an attractive alternative to considerably relax these constraints, but it is not clear whether the proximity effect would be effective in heterostructures involving cuprates and topological insulators...
August 8, 2014: Physical Review Letters
Seung Hwan Hong, Jin Mo Bok, Wentao Zhang, Junfeng He, X J Zhou, C M Varma, Han-Yong Choi
There is an enormous interest in the renormalization of the quasiparticle (qp) dispersion relation of cuprate superconductors both below and above the critical temperature T_{c} because it enables the determination of the fluctuation spectrum to which the qp's are coupled. A remarkable discovery by angle-resolved photoemission spectroscopy (ARPES) is a sharp low-energy feature (LEF) in qp spectra well below the superconducting energy gap but with its energy increasing in proportion to T_{c} and its intensity increasing sharply below T_{c}...
August 1, 2014: Physical Review Letters
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