Publication Date

11-15-2018

Department

Ames Laboratory; Physics and Astronomy

Campus Units

Physics and Astronomy, Ames Laboratory

OSTI ID+

1487218

Report Number

IS-J 9823

DOI

10.1103/PhysRevB.98.184506

Journal Title

Physical Review B

Volume Number

98

Issue Number

18

First Page

184506

Abstract

Upon doping with Tl the narrow band-gap semiconductor PbTe exhibits anomalously high-temperature superconductivity despite a very low carrier-density as well as signatures of the Kondo effect despite an absence of magnetic moments. These phenomena have been explained by invoking 2e fluctuations of the valence of the Tl dopants, but a direct measurement of the mixed valency implied by such a mechanism has not been reported to date. In this work we present the unambiguous observation of multiple valences of Tl in Tl-doped PbTe via photoemission spectroscopy measurements. It is shown via a quantitative analysis that the suppression of the carrier density in compositions exhibiting superconductivity and Kondo-like behavior can be accounted for by mixed valency, thus arguing against a self-compensation scenario proposed elsewhere for this material and strengthening the case for valence fluctuation models. In addition to the identification of Tl+ and Tl3+ a possible third intermediate local charge-density is suggested by full fits to the data, the origins of which are also discussed but remain unclear.

DOE Contract Number(s)

AC02-07CH11358; FA9550-09-1-0583; DMR 9212658

Language

en

Department of Energy Subject Categories

74 ATOMIC AND MOLECULAR PHYSICS

Publisher

Iowa State University Digital Repository, Ames IA (United States)

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