Superconductivity, structure, and charge disproportionation in gold chalcogenides

Nominal Au2+ compounds can be a rich source of physics, including superconductivity and charge density waves, due to gold’s tendency toward charge disproportionation (Au2+ → Au1+ + Au3+) which generates structural and charge modulation. The known compound AuTe2 calverite is structurally unique due its incommensurate crystal structure and the occurrence of [Te2]2- dimers, and research has shown the induction of superconductivity by pressure or by cation doping to be concomitant with the breaking of these dimers [1]. The putative underlying cause of both dimerization and superconductivity in calaverite is charge disproportionation of nominally Au2+ on a triangular sublattice. Moreover, a new binary compound AuTe has been predicted to be stable in a narrow range [1], but remains unsynthesized. Both AuTe and AuTe2 have half-silver analogues, AuAgTe2 and AuAgTe4, which represent possible structural extremes of +1/+3 cation charge modulation.

We seek a graduate student to investigate these and similar gold chalcogenides: specifically, the student will perform synthesis, characterization, and measurement of known and new compounds including those with chalcogen substitution, and will collaborate with in-house high-pressure and computational groups.

[1] S.V. Streltsov, V.V. Roizen, A.V. Ushakov, A.R. Oganov, and D.I. Khomskii
Old puzzle of incommensurate crystal structure of calaverite AuTe2 and predicted stability of novel AuTe compound
PNAS 115, 9945 (2018)

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