Competition of superconductivity with the structural transition in Mo3Sb7

TL;DR

This study investigates how pressure influences the competition between superconductivity and structural transitions in Mo3Sb7, revealing a pressure-induced phase coexistence and the interplay with magnetism.

Contribution

It provides the first detailed pressure-dependent analysis of structural and superconducting transitions in Mo3Sb7, supported by first-principles calculations.

Findings

Pressure enhances Tc up to 6 K at high pressures.

Structural transition Ts is suppressed and eventually replaced by a cubic phase.

Superconductivity and structural transition compete, following the Bilbro-McMillan relation.

Abstract

Prior to the superconducting transition at Tc = 2.3 K, Mo3Sb7 undergoes a symmetry-lowering, cubic-to-tetragonal structural transition at Ts = 53 K. We have monitored the pressure dependence of these two transitions by measuring the resistivity of Mo3Sb7 single crystals under various hydrostatic pressures up to 15 GPa. The application of external pressure enhances Tc but suppresses Ts until Pc ~ 10 GPa, above which a pressure-induced first order structural transition takes place and is manifested by the phase coexistence in the pressure range 8 < P < 12 GPa. The cubic phase above 12 GPa is also found to be superconducting with a higher Tc =6 K that decreases slightly with further increasing pressure. The variations with pressure of Tc and Ts satisfy the Bilbro-McMillan equation, i.e. Tc^nTs^(1-n) = constant, thus suggesting the competition of superconductivity with the structural transition that has been proposed to be accompanied with a spin-gap formation at Ts. This scenario is supported by our first-principles calculations which imply the plausible importance of magnetism that competes with the superconductivity in Mo3Sb7.