Fragile structural transition in Mo3Sb7

TL;DR

This study investigates how slight doping with Cr, Ru, or Te affects the structural transition and superconductivity in Mo3Sb7, revealing the transition's fragility and the independence of superconductivity from the tetragonal phase.

Contribution

It provides new insights into the sensitivity of the structural transition to electron doping and its relationship with superconductivity in Mo3Sb7.

Findings

Ru and Te doping suppress the structural transition

Cr doping slightly reduces the transition temperature

All dopants suppress superconductivity

Abstract

Mo$_3$Sb$_7$ single crystals lightly doped with Cr, Ru, or Te are studied in order to explore the interplay between superconductivity, magnetism, and the cubic-tetragonal structural transition. The structural transition at 53\,K is extremely sensitive to Ru or Te substitution which introduce additional electrons, but robust against Cr substitution. No sign of a structure transition was observed in superconducting Mo$_{2.91}$Ru$_{0.09}$Sb$_7$ and Mo$_3$Sb$_{6.975}$Te$_{0.025}$. In contrast, 3at\% Cr doping only slightly suppresses the structural transition to 48\,K while leaving no trace of superconductivity above 1.8\,K. Analysis of magnetic properties suggests that the interdimer interaction in Mo$_3$Sb$_7$ is near a critical value and essential for the structural transition. All dopants suppress the superconductivity of Mo$_3$Sb$_7$. The tetragonal structure is not necessary for superconductivity.