Specific heat studies of pure Nb3Sn single crystals at low temperature

TL;DR

This study investigates the low-temperature specific heat of pure Nb3Sn crystals, revealing details about martensitic and superconducting transitions, including their nature, temperature correlation, and a single superconducting energy gap.

Contribution

The paper provides new insights into the thermodynamic nature of the martensitic transition and its relation to superconductivity in high purity Nb3Sn crystals.

Findings

Martensitic transition shows no hysteresis, suggesting a weak first or second order transition.

Inverse correlation observed between martensitic and superconducting transition temperatures.

Presence of a single superconducting energy gap at low temperatures.

Abstract

Specific heat measurements performed on high purity vapor-grown Nb$_3$Sn crystals show clear features related to both the martensitic and superconducting transitions. Our measurements indicate that the martensitic anomaly does not display hysteresis, meaning that the martensitic transition could be a weak first or a second order thermodynamic transition. Careful measurements of the two transition temperatures display an inverse correlation between both temperatures. At low temperature specific heat measurements show the existence of a single superconducting energy gap feature.