Lattice dynamics in the FeSi-based family of superconductors

TL;DR

This study investigates the lattice dynamics of FeSi-based superconductors LaFeSiH and LaFeSiO using Raman spectroscopy and first-principles calculations, revealing unique vibrational features and structural insights related to their superconducting properties.

Contribution

It provides new insights into the lattice vibrations and structural characteristics of FeSi-based superconductors, highlighting their electron-phonon interactions and potential non-centrosymmetry.

Findings

Fe-dominated Raman modes reflect chemical peculiarities

Enhanced electron-phonon coupling observed in some modes

Structural subtleties suggest LaFeSiH may be non-centrosymmetric

Abstract

The lattice dynamics of the superconducting materials LaFeSiH and LaFeSiO as well as their intermetallic precursor LaFeSi are investigated by polarized Raman spectroscopy and first-principles calculations, together with X-ray and advanced electron diffraction techniques for their structural analysis. We find that the Fe-dominated Raman-active modes reflect the chemical peculiarities of these silicides compared to their pnictide counterparts, with enhanced structural couplings between the FeSi layer and the spacer that can be related to the ionic vs covalent character of the latter. In addition, we find signatures of enhanced electron-phonon coupling for some of the Raman-active modes. Beyond that, our study reveals intriguing Fe-based Raman features as well as structural subtleties in LaFeSiH suggesting that this superconductor may formally be non-centrosymmetric.