We present a comprehensive investigation of the structural, electrical transport, and magnetic properties of FeSex (x = 1.14, 1.18, 1.23, 1.28, and 1.32) to unravel the mechanism of the metal-insulator transition observed in these systems. For this, we systematically evaluated the structural parameters of FeSex as a function of Se concentration and temperature. We observe increased lattice constants and cell volume with increased Se concentration. On the other hand, the temperature-dependent XRD studies suggest unusual lattice change around the metal-insulator (MI) transition temperature of the respective compositions. This remarkable observation suggests that the anomalous lattice effect originates the MI transition in these systems. Additionally, our density of states (DOS) calculations on FeSe1.14 qualitatively explain the MI transition, as the low-temperature (50 K) structure DOS suggests a metallic nature and the high-temperature (300 K) structure DOS shows a gap near the Fermi level.
@article{arxiv.2501.12724,
title = {Anomalous Lattice Effect Originated Metal-Insulator Transition in FeSe$_x$},
author = {Shubham Purwar and Shinjini Paul and Kritika Vijay and R. Venkatesh and Soma Banik and P. Mahadevan and S. Thirupathaiah},
journal= {arXiv preprint arXiv:2501.12724},
year = {2025}
}