# Gapless regime in the charge density wave phase of the finite dimensional Falicov-Kimball model

## TL;DR

This paper investigates the gapless regime in the charge density wave phase of the finite-dimensional Falicov-Kimball model, revealing how localized states and subgap density of states influence charge transport.

## Contribution

It demonstrates the existence of a stable gapless phase in the charge density wave regime and links it to localized single-particle excitations and subgap states.

## Key findings

- Presence of a stable gapless phase with high density of states at the Fermi level.
- Strong localization indicated by inverse participation ratio analysis.
- Enhanced charge transport in heterostructures with the Falicov-Kimball system.

## Abstract

The ground-state density of states of the half-filled Falicov-Kimball model contains a charge-density-wave gap. At finite temperature, this gap is not immediately closed, but is rather filled in by subgap states. For a specific combination of parameters, this leads to a stable phase where the system is in an ordered charge-density-wave phase, but there is high density of states at the Fermi level. We show that this property can be, in finite dimensions, traced to a crossing of sharp states resulting from the single particle excitations of the localized subsystem. The analysis of the inverse participation ratio points to a strong localization in the discussed regime. However, the pronounced subgap density of states can still lead to a notable increase of charge transport through a finite size system. We show this by focusing on the transmission in heterostructures where a Falicov-Kimball system is sandwiched between two metallic leads.