Abstract
Electronic conduction in () compounds with the fcc -type structure originates from hopping of localized unpaired electrons () among widely separated tetrahedral metal clusters. We show that under pressure these systems transform from Mott insulators to a metallic and superconducting state with and 5.8 K at 13 and 11.5 GPa for and , respectively. The occurrence of superconductivity is shown to be connected with a pressure-induced decrease of the octahedral distortion and simultaneous softening of the phonon associated with bonds.
- Received 30 April 2004
DOI:https://doi.org/10.1103/PhysRevLett.93.126403
©2004 American Physical Society