Superconductivity near the vibrational mode instability in MgCNi3

TL;DR

This study uses density functional calculations to analyze electron-phonon interactions in MgCNi3, predicting strong coupling and vibrational instabilities that influence its superconducting properties.

Contribution

It provides detailed phonon calculations revealing the dominant Ni atom displacements and highlights the importance of anharmonic effects in understanding superconductivity in MgCNi3.

Findings

Predicted electron-phonon coupling constant λ=1.51

Identified key phonon modes involving Ni displacements

Found vibrational instabilities suggesting anharmonic effects are significant

Abstract

To understand the role of electron-phonon interaction in superconducting MgCNi$_{3}$ we have performed density functional based linear response calculations of its lattice dynamical properties. A large coupling constant $% \lambda $= 1.51 is predicted and contributing phonons are identified as displacements of Ni atoms towards octahedral interstitials of the perovskite lattice. Instabilities found for some vibrational modes emphasize the role of anharmonic effects in resolving experimental controversies.