Strong Electron-Phonon Coupling Superconductivity Induced by a Low-lying Phonon in IrGe

TL;DR

This study reveals that IrGe exhibits strong electron-phonon coupling due to a low-lying phonon, leading to its high superconducting transition temperature among similar compounds.

Contribution

It demonstrates the link between low-lying phonons and high Tc in IrGe, highlighting the role of strong electron-phonon coupling in this superconductor.

Findings

IrGe has a high Tc of 4.7 K among MGe compounds.

IrGe exhibits an anomalously low Debye temperature.

Strong coupling superconductivity is confirmed by specific-heat measurements.

Abstract

The physical properties of the previously reported superconductor IrGe and the Rh1-xIrxGe solid solution are investigated. IrGe has an exceptionally high superconducting transition temperature (Tc = 4.7 K) among the isostructural 1:1 late-metal germanides MGe (M = Rh, Pd, Ir and Pt). Specific-heat measurements reveal that IrGe has an anomalously low Debye temperature, originating from a low-lying phonon, compared to the other MGe phases. A large jump at Tc in the specific-heat data clearly indicates that IrGe is a strong coupling superconductor. In the Rh1-xIrxGe solid solution, a relationship between an anomalous change in lattice constants and the Debye temperature is observed. We conclude that the unusually high Tc for IrGe is likely due to strong electron-phonon coupling derived from the presence of a low-lying phonon.