Regensburg 2007 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 8: Superconductivity - Poster Session
TT 8.5: Poster
Monday, March 26, 2007, 14:00–17:45, Poster A
Anomalous magnetic field dependence of the superconducting condensation energy in YBa2Cu3O7 single crystals — •P. Popovich1,2, C. Meingast1, S. Tajima3, and T. Masui3 — 1Forschungszentrum Karlsruhe, Institute for Solid-State Physics, 76021 Karlsruhe, Germany — 2Fakultät für Physik, Universität Karlsruhe, Germany — 3ISTEC, Tokyo, Japan
The anisotropic magnetostriction and thermal expansion of untwinned YBa2Cu3O7 single crystals have been studied using capacitance dilatometry for H||c along all crystallographic axes. The thermodynamical analysis is possible due to the high crystal quality. The magnetostriction coefficient λi = 1/LidLi/dH (i=a,b,c) is reversible above 55 K, providing important information about the pressure dependencies of the thermodynamical critical field Hc(T).
The magnetic field dependence of the zero-temperature superconducting condensation energy is obtained by using the fact that the length (volume) difference between normal and superconducting states, Ln-Ls, provides a direct measure of the uniaxial pressure (hydrostatic pressure) dependence of the superconducting condensation energy. In conventional BCS superconductors, the superconducting condensation energy, as well as the magnitude of Ln-Ls, decreases monotonically with increasing field due to the increasing density of normal-state vortex cores. We find practically no field dependence of Ln-Ls as T approaches zero, which implies that the superconducting pairing energy is nearly field-independent in magnetic field up to 10 T.