First principles correspondence of a second type of phonon anomaly along [211] to the Fermi nesting features and associated electron-phonon interactions in Ni$_2$FeGa

TL;DR

This study uses first principles calculations to link a phonon anomaly in Ni₂FeGa along [211] to Fermi surface nesting and electron-phonon interactions, explaining structural modulations observed experimentally.

Contribution

It provides a detailed first-principles analysis connecting phonon anomalies to Fermi surface nesting and electron-phonon coupling in Ni₂FeGa, a novel insight into its structural behavior.

Findings

Fermi surface nesting vectors match phonon anomaly wavevectors

Significant electron-phonon coupling observed in the austenite phase

Lattice coupling between phonon modes contributes to the anomaly

Abstract

First principles calculation supports the occurence of a phonon anomaly along [211] in Ni$_2$FeGa that was observed experimentally for the first time as structural modulations along [211] direction. Fermi surface scans have been performed in both austenite and martensite phase to observe the possible Fermi nesting features in the system. The magnitude of observed Fermi surface nesting vectors in (211) plane exactly match the phonon anomaly wavevectors along [211] direction. Electron-phonon calculations in the austenite phase shows that there is significant electron-phonon coupling in the system which may arise out of the lattice coupling between lower acoustic phonon modes and higher optical phonon modes and also because of strong Fermi surface nesting features observed in the system.