Transition from Mott insulator to superconductor in GaNb$_{4}$Se$_{8}$ and GaTa$_{4}$Se$_{8}$ under high pressure

M. M. Abd-Elmeguid; B. Ni; D. I. Khomskii; R. Pocha; D. Johrendt; X. Wang; K. Syassen

doi:10.1103/PhysRevLett.93.126403

paper

Transition from Mott insulator to superconductor in GaNb $_{4}$ Se $_{8}$ and GaTa $_{4}$ Se $_{8}$ under high pressure

arXiv:cond-mat/0504284 · doi:10.1103/PhysRevLett.93.126403

Abstract

Electronic conduction in GaM $_{4}$ Se $_{8}$ (M=Nb;Ta) compounds with the fcc GaMo $_{4}$ S $_{8}$ -type structure originates from hopping of localized unpaired electrons (S=1/2) among widely separated tetrahedral M $_{4}$ metal clusters. We show that under pressure these systems transform from Mott insulators to a metallic and superconducting state with T $_{C}$ =2.9 and 5.8K at 13 and 11.5GPa for GaNb $_{4}$ Se $_{8}$ and GaTa $_{4}$ Se $_{8}$ , respectively. The occurrence of superconductivity is shown to be connected with a pressure-induced decrease of the MSe $_{6}$ octahedral distortion and simultaneous softening of the phonon associated with MSe-bonds.

10 pages, 5 figures

Transition from Mott insulator to superconductor in GaNb4​Se8​ and GaTa4​Se8​ under high pressure

Abstract

Transition from Mott insulator to superconductor in GaNb $_{4}$ Se $_{8}$ and GaTa $_{4}$ Se $_{8}$ under high pressure