F-electron spectral function of the Falicov-Kimball model in infinite dimensions: the half-filled case

TL;DR

This paper calculates the f-electron spectral function of the Falicov-Kimball model in infinite dimensions using a Keldysh formalism, revealing temperature-dependent spectral features for different interaction strengths.

Contribution

It applies a Keldysh-based formalism to compute spectral functions for the Falicov-Kimball model on different lattices at half filling, analyzing numerical accuracy and temperature effects.

Findings

Spectral function becomes narrow and single-peaked at small U

A gap opens and peaks broaden at large U

Results depend on lattice type and temperature

Abstract

The f-electron spectral function of the Falicov-Kimball model is calculated via a Keldysh-based many-body formalism originally developed by Brandt and Urbanek. We provide results for both the Bethe lattice and the hypercubic lattice at half filling. Since the numerical computations are quite sensitive to the discretization along the Kadanoff-Baym contour and to the maximum cutoff in time that is employed, we analyze the accuracy of the results using a variety of different moment sum-rules and spectral formulas. We find that the f-electron spectral function has interesting temperature dependence becoming a narrow single-peaked function for small U and developing a gap, with two broader peaks for large U.