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The temperature dependence of the upper critical magnetic field (Hc2) in a BaFe1.84Co0.16As2 single crystal was determined via resistivity, for the inter-plane (H^ab) and in-plane (H//ab) directions in pulsed and static magnetic fields of…

Superconductivity · Physics 2015-05-13 M. Kano , Y. Kohama , D. Graf , F. F. Balakirev , A. S. Sefat , M. A. McGuire , B. C. Sales , D. Mandrus , S. W. Tozer

A study of the dependence of the heat capacity Cp(alpha) on field angle in LuNi2B2C reveals an anomalous disorder effect. For pure samples, Cp(alpha) exhibits a fourfold variation as the field H < Hc2 is rotated in the [001] plane, with…

We address the question of whether anisotropic superconductivity is compatible with the evidently weak sensitivity of the critical temperature Tc to sample quality in the high-Tc copper oxides. We examine this issue quantitatively by…

Condensed Matter · Physics 2009-10-22 R. J. Radtke , K. Levin , H. -B. Schuttler , M. R. Norman

By recognizing the vital importance of two-hole Cooper pairs (CPs) in addition to the usual two-electron ones in a strongly-interacting many-electron system, the concept of CPs was re-examined with striking conclusions. Based on this,…

Superconductivity · Physics 2009-11-11 M. de Llano , M. Grether

We present a detailed study of the BCS pairing transition in a trapped polarized dipolar Fermi gas. In the case of a shallow nearly spherical trap, we find the decrease of the transition temperature as a function of the trap aspect ratio…

Other Condensed Matter · Physics 2009-11-10 M. A. Baranov , L. Dobrek , M. Lewenstein

We review the empirical scenario emerging from the measured doping dependence of the transition temperature and the anisotropy parameter $% \gamma $ $=\xi _{ab}/\xi_{c}$, defined as the ratio of the correlation lengths parallel and…

Superconductivity · Physics 2007-05-23 T. Schneider

The metallic state of high temperature cuprate superconductors is markedly different from that of textbook metals. The origin of this unconventional state, characterized by unusual and distinct temperature dependences in the transport…

We report angle-resolved photoemission spectroscopy measurements of the excitation gap in underdoped superconducting thin films of Bi_2Sr_2Ca_{1-x}Dy_xCu_2O_{8+d}. As Tc is reduced by a factor of 2 by underdoping, the superconducting state…

Superconductivity · Physics 2009-10-28 J. M. Harris , Z. -X. Shen , P. J. White , D. S. Marshall , M. C. Schabel , J. N. Eckstein , I. Bozovic

For the Cooper/BCS model interaction in superconductors (SCs) it is shown: a) how BCS-Bose crossover picture transition temperatures Tc, defined self-consistently by both the gap and fermion-number equations, require unphysically large…

Superconductivity · Physics 2007-05-23 M. de Llano , F. J. Sevilla , M. A. Solis , J. J. Valencia

The unconventional magnetotransport at the interface between transition-metal oxides $LaAlO_3$ (LAO) and $SrTiO_3$ (STO) is frequently related to mobile electrons interacting with localized magnetic moments. However nature and properties of…

Mesoscale and Nanoscale Physics · Physics 2017-05-30 N. Bovenzi , M. Diez

We deal with a model for high-temperature superconductivity which maintains that in cuprates electrons running in the copper oxide layers, found in lattice of these materials, form spin-singlet bonds with electrons running in the…

Superconductivity · Physics 2007-05-23 P. Brovetto , V. Maxia

This paper reports specific-heat measurements on superconducting MgB2 in magnetic fields to 9 T. In zero magnetic field the data can be fitted to a two-gap model, which is a generalization of a semi-empirical model for strong-coupled,…

Superconductivity · Physics 2007-05-23 R. A. Fisher , F. Bouquet , N. E. Phillips , D. G. Hinks , J. D. Jorgensen

Data on macroscopic superconducting anisotropy of MgB$_2$ are reviewed. The data are described within a weak coupling two-gaps anisotropic s-wave model of superconductivity. The calculated ratio of the upper critical fields…

Superconductivity · Physics 2009-11-07 V. G. Kogan , S. L. Bud'ko

The symmetry of the superconducting order parameter, or simply the ``gap'', provides certain constraints on the actual mechanism that gives rise to pairing and ultimately to superconductivity. In this work we show how superconducting phases…

Superconductivity · Physics 2025-05-14 Pramodh Senarath Yapa , Xinyu Guo , Joseph Maciejko , Frank Marsiglio

Superconductivity was recently observed in the iron-arsenic-based compounds with a superconducting transition temperature (Tc) as high as 56K [1-7], naturally raising comparisons with the high Tc copper oxides. The copper oxides have…

Superconductivity · Physics 2009-11-13 H. Q. Yuan , J. Singleton , F. F. Balakirev , S. A. Baily , G. F. Chen , J. L. Luo , N. L. Wang

Photoexcited quasiparticle relaxation dynamics are investigated in a $YBa_{2}Cu_{3}O_{7-\delta}$ superconductor as a function of doping $\delta$ and temperature $T$ using ultrafast time-resolved optical spectroscopy. A model calculation is…

Superconductivity · Physics 2009-10-31 V. V. Kabanov , J. Demsar , B. Podobnik , D. Mihailovic

The dependence of the superconducting gaps in epitaxial Ba(Fe_{1-x}Co_{x})_2As_2 thin films on the nominal doping x (0.04 \leq x \leq 0.15) was studied by means of point-contact Andreev-reflection spectroscopy. The normalized conductance…

Superconductivity · Physics 2013-12-10 P. Pecchio , D. Daghero , G. A. Ummarino , F. Kurth , B. Holzapfel , K. Iida , R. S. Gonnelli

An approach is proposed to nuclear pairing at finite temperature and angular momentum, which includes the effects of the quasiparticle-number fluctuation and dynamic coupling to pair vibrations within the self-consistent quasiparticle…

Nuclear Theory · Physics 2009-11-13 N. Dinh Dang , N. Quang Hung

We compare theoretical results for electron spin resonance (ESR) properties of the Heisenberg-Ising Hamiltonian with ESR experiments on the quasi-one-dimensional magnet Cu(py)$_2$Br$_2$ (CPB). Our measurements were performed over a wide…

We investigate the superconducting-gap anisotropy in one of the recently discovered BiS$_2$-based superconductors, NdO$_{0.71}$F$_{0.29}$BiS$_2$ ($T_c$ $\sim$ 5 K), using laser-based angle-resolved photoemission spectroscopy. Whereas the…