title: Evidence for charge Kondo effect in superconducting Tl-doped PbTe.
abstract: We report results of low-temperature thermodynamic and transport measurements of Pb1-xTlxTe single crystals for Tl concentrations up to the solubility limit of approximately x=1.5%. For all doped samples, we observe a low-temperature resistivity upturn that scales in magnitude with the Tl concentration. The temperature and field dependence of this upturn are consistent with a charge Kondo effect involving degenerate Tl valence states differing by two electrons, with a characteristic Kondo temperature T(K) approximately 6 K. The observation of such an effect supports an electronic pairing mechanism for superconductivity in this material and may account for the anomalously high T(c) values.
authors.affiliation: Department of Materials Science and Engineering and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305-4045, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Matsushita
authors.forename: H
authors.initials: H
authors.lastname: Bluhm
authors.forename: T H
authors.initials: TH
authors.lastname: Geballe
authors.forename: I R
authors.initials: IR
authors.lastname: Fisher