Tracking flat bands via phonon-mediated interband scattering

TL;DR

This paper presents a method to detect flat bands near the Fermi level in materials by analyzing temperature-dependent resistivity caused by phonon-mediated interband scattering, providing a universal transport signature.

Contribution

It introduces a phenomenological model linking resistivity behavior to flat band proximity, enabling detection of flat bands through transport measurements.

Findings

Resistivity shows sub- or superlinear temperature dependence when flat bands are near $E_F$.

The model successfully explains transport behaviors in various flat-band materials.

Proposes a simple method for flat band detection using electrical resistivity data.

Abstract

Flat-band (FB) materials have emerged as promising platforms for exploring exotic quantum phases. While numerous candidates have recently been identified through spectroscopic techniques such as angle-resolved photoemission spectroscopy, central challenges remain on how to tune FBs towards the Fermi level $E_F$ and to understand their impact on low-energy excitations probed in electronic transport experiments. Here, we show that, by attributing the temperature dependence of the electrical resistivity at elevated temperatures to electron-phonon interband scattering, one can infer the position of FBs near $E_F$ across diverse material classes. As charge carriers scatter off phonons, interband transitions into FB states lead to distinctive sub- or superlinear resistivity at elevated temperatures, governed by the proximity of the FB to $E_F$. Our phenomenological model captures these universal transport behaviors observed across several recently studied FB compounds and offers a simple, broadly applicable method for detecting flat bands.