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, K. Syassen
DOI 10.1103/PhysRevLett.93.126403 · Physical Review Letters
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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 M−Se bonds.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| GaNb4Se8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 2.9 | 13 GPa | onset |
| GaTa4Se8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 5.8 | 11.5 GPa | onset |
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