Sign reversal of the Hall effect belowTcin untwinned single-crystalYBa2

Abstract

Because of possible effects from (110) twin planes and a-b anisotropy in YBa&Cu307 z, measurements on untwinned crystals are desirable. We have measured the Hall effect and resistivity simultaneously in untwinned single-crystal YBa2Cu307 -$ with a superconducting transition temperature T, =93 K, with the magnetic field along the c axis. Below T"the measured Hall resistivity reverses sign, becoming negative over a range of temperature and magnetic field, and the location and magnitude of the minimum is similar to that measured previously by others on twinned samples. These results show that the negative Hall resistivity is not caused by twin planes inducing guided vortex motion or vortex pinning. In addition, the exponent characterizing a scaling relation of the longitudinal to the Hall resistivity has a value consistent with that measured on thin films.

Non-Ohmic Hall resistivity observed above the critical temperature in the high-temperature superconductorYBa2Cu3O7−δ

“…It leads to both the sharp drop of the Hall resistivity and to its sign change. 17,[33][34][35][36] The negative contribution to xy is frequently ascribed, both by theoretical and experimental work, to fluctuating superconducting pairs, essentially to those of the Aslamazov-Larkin ͑AL͒ process. [37][38][39][40][41] The Hall resistivity, however, does not diverge toward lower temperatures, but, on the contrary, vanishes.…”

Paramagnetic current and dissipative vortex motion in type-II superconductors

“…[17][18][19][20][21][22][23] They suggested that, if the drag force has components along v L and v L ϫẑ analogous to the theory of the superfluid, 24-27 the Hall angle inversion can then be explained simply from the force balance equation for a single vortex, assuming that the NV result for a very-lowtemperature region is valid for the high-temperature region near T c . Contrary to the Ferrell's theory 28 which assumes that there exists a drag force due to the Andreev reflection of quasiparticles by the diamagnetic current outside the vortex core, our theory, based on no presumption, shows that dissipation due to the drag force occurs in the normal core alone.…”

Eilenberger Approach to the Vortex State in Iron Pnictide Superconductors

“…(6,7)] are solved by the Fast Fourier Transform (FFT) method for triangular FLL [55]. This method is reasonable for the dense FLL, discussed in this paper.…”

“…Therefore, the impurity renormalization correction in Eqs. (6) and (7), averaged over the Fermi surface, can be reduced to averages over the polar angle θ,i.e. ... =(1/2π) ...dθ.…”

“…Some experiment executed by Li et al [1] in response to a suggestion by Klemm [2] tested the phase of the wave function in Bi 2 Sr 2 CaCu 2 O 8 and revived the s-wave viewpoint [3,4]], which, although championed by Dynes's group [4], had been out of favor even for Bi 2 Sr 2 CaCu 2 O 8 , although not disproven. This experiment once more created uncertainty over whether the superconducting pairs are consistent with s-wave or d-wave superconductivity (Van Harlingen [5], Ginsberg [6], Tsuei and Kirtley [7]). …”