A dimensional characteristic in the specific heat of high temperature superconductors

Abstract

The specific heat C of superconductors is strongly depressed just below the transition temperature by an increase of the magnetic field ΔB. A measurement of the function | ∂( C/ T)/ ∂B| for different magnetic fields at T≈ T c, which can be approximated by a Lorentzian of half-height width ΔT( B) αB n , is found to be a direct way of determining the dimensionality of a superconducting system in the LLL (lowest Landau level) approximation, with n= 1 2 D and n= 2 3 for 3D. No baseline subtraction is required. Examples are given using high resolution specific heat measurements between 0 and 16 tesla on YBa 2Cu 3O 7−δ (YBCO) and Bi 2Sr 2CaCu 2O 8 (BSCCO) single crystals. The temperature T cB( B) of the minimum of | ∂( C/ T)/ ∂B| can be related to the mean-field critical temperature T c( B) in the framework of the theory of Tešanović at high fields.