Evidence for charge Kondo effect in superconducting Tl-doped PbTe

TL;DR

This study provides evidence of a charge Kondo effect in Tl-doped PbTe, linking it to the material's superconductivity and high T_c, through low-temperature thermodynamic and transport measurements.

Contribution

It demonstrates the presence of a charge Kondo effect in Tl-doped PbTe, suggesting an electronic pairing mechanism for its superconductivity, a novel insight into this material.

Findings

Resistivity upturn scales with Tl concentration

Charge Kondo effect consistent with valence degeneracy

Kondo temperature around 6 K

Abstract

We report results of low-temperature thermodynamic and transport measurements of Pb_{1-x}Tl_{x}Te 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 ~ 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.