J. Buan

Determination of the pairing state of high-Tc superconductors through measurement of the transverse magnetization☆

Abstract The angular dependence of the in-plane, off-axis magnetization of a LuBa 2 Cu 3 O 7−δ single crystal has been measured, and the amplitude of the Fourier component with angular period π/2 has been found to be smaller than expectations for pure d -wave pairing. The results are consistent with isotropic pairing, but do not rule out nodeless anisotropic pairing.

Analysis of the specific heat of high-Tc superconductors in magnetic fields☆

Abstract We have performed high-resolution specific-heat measurements on an untwinned, high-quality single crystal of LuBa2Cu3O7−x, near the normal-superconducting transition temperature, in applied magnetic fields up to 5 T, along the c-axis. The data has been analyzed in terms of the finite-size scaling approach, Inderhees, et al., (PRL 66, 232, (1991)). We have found that this idea does not adequately describe our results. The problems associated with this model will be detailed. Recently, a model proposed by Tesanovic et al. (PRL 69, 3563 (1992)) has been utilized with some success.

Probing of the pairing state of HTSCs utilizing a‐b plane magnetization anisotropy (abstract)

We have performed measurements of the a‐b plane longitudinal and transverse magnetization anisotropy on an untwinned, high quality single crystal of LuBa2Cu3O7−x in magnetic fields below Hc1 as a function of temperature, from 2 K to the transition temperature and the angle between the field and a fixed direction in the a‐b plane. When the superconducting order parameter has nodes on the Fermi surface, such as the case of the spin‐singlet dx2−y2 order parameter, nonlinear effects associated with low‐energy quasiparticles should become important.1 It was pointed out by Yip and Sauls that these effects will be most important at low temperatures. They should be observable in a measurement of the anisotropy of the magnetization or the magnetic torque. The magnetization is predicted to develop an anisotropic component transverse to the applied field. Anisotropic transverse magnetization with dx2−y2 symmetry is not seen in the temperature regime 5 to 25 K. Our results set stringent limits on the anisotropy of th...