Internal Friction Related to Carriers in High‐ T<inf>c</inf>Superconductors

Abstract

For both BiSrCaCuO and TlBaCaCuO samples, internal frictions (Q −l ) in the kHz range reveal a plateau (Q p −1 ) above T c and drop rapidly below T c with the turning points at T c . This kind of anomaly cannot be observed for nonsuperconducting samples. Moreover, it is discovered that Q p −1 is nearly proportional to the Hall carrier density for Y(Pr)BaCuO with various Pr content. These results show that the drop of Q −1 below T c is closely related to superconducting condensation. The mechanism of Q p −1 may be attributed to the carrier jump induced by the stress‐induced reorientation of the polaron‐like distortions around the carriers. Further, taking into account the smearing of the superconducting gap structure resulting from the recombination of quasi‐particles and modifying the BCS relative jump rate the calculated results of internal friction below T c are in fairly good agreement with experimental data. The superconducting gap Δ and the damping rate Γ for both BiSrCaCuO and TlBaCaCuO have also been obtained, they are in accordance with those got by tunneling spectrum and NMR methods, etc. Copyright © 1993 WILEY‐VCH Verlag GmbH & Co. KGaA