From Wavefunction Collapse to Superconductivity: Evolution of the Electronic State in Compressed GaNb4Se8

TL;DR

This study explores how pressure induces a transition from localized to metallic and superconducting states in GaNb4Se8, revealing a hierarchy between electronic delocalization and structural changes.

Contribution

It provides the first detailed pressure-dependent transport analysis of GaNb4Se8, highlighting the decoupling of electronic and structural transitions and the emergence of superconductivity.

Findings

Resistivity follows Efros-Shklovskii variable-range hopping at low pressures.

Metallic transport begins near ~5 GPa.

Superconductivity appears at higher pressures with coherence length ~80-90 Å.

Abstract

Understanding how electronic transport evolves from localized to itinerant regimes in correlated cluster solids remains an important challenge in condensed-matter physics. Here we investigate the pressure-dependent transport properties of the lacunar spinel GaNb4Se8, a cluster Mott insulator at ambient conditions. At low pressures, the resistivity follows Efros-Shklovskii variable-range hopping, indicating Coulomb-gap-controlled carrier localization (x ~ 6.1 Angstrom). A crossover toward metallic transport begins near ~ 5 GPa, whereas a crystallographic transition from the cubic phase to a monoclinic C2 phase occurs at significantly higher pressure (~ 20 GPa), establishing a hierarchy characterized by the decoupling of electronic delocalization from structural symmetry change. At higher pressures, superconductivity (xi(0) ~ 80-90 Angstrom) emerges from the correlated metallic regime. These results identify GaNb4Se8 as a platform for studying correlation-controlled transport evolution in cluster-based solids.