Transition from Mott Insulator to Superconductor in GaNb4Se8 and GaTa4Se8 under High Pressure

M. M. Abd-Elmeguid, B. Ni, D. I. Khomskii, R. Pocha, D. Johrendt, X. Wang, and K. Syassen
Phys. Rev. Lett. 93, 126403 – Published 16 September 2004

Abstract

Electronic conduction in GaM4Se8 (M=Nb,Ta) compounds with the fcc GaMo4S8-type structure originates from hopping of localized unpaired electrons (S=12) among widely separated tetrahedral M4 metal clusters. We show that under pressure these systems transform from Mott insulators to a metallic and superconducting state with TC=2.9 and 5.8 K at 13 and 11.5 GPa for GaNb4Se8 and GaTa4Se8, respectively. The occurrence of superconductivity is shown to be connected with a pressure-induced decrease of the MSe6 octahedral distortion and simultaneous softening of the phonon associated with MSe bonds.

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  • Received 30 April 2004

DOI:https://doi.org/10.1103/PhysRevLett.93.126403

©2004 American Physical Society

Authors & Affiliations

M. M. Abd-Elmeguid1, B. Ni1, D. I. Khomskii1,*, R. Pocha2, D. Johrendt2, X. Wang3, and K. Syassen3

  • 1II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
  • 2Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus D), 81377 München, Germany
  • 3Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany

  • *Also at Groningen University, Nijenborgh 4, 9722 AG Groningen, The Netherlands.

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Vol. 93, Iss. 12 — 17 September 2004

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