Theoretical study of the optical conductivity of $\alpha'-NaV_2O_5$

TL;DR

This study uses finite temperature diagonalization to explain the anisotropic optical conductivity of $ ext{NaV}_2 ext{O}_5$ through a quarter-filled t-J-V model, highlighting the roles of Coulomb interactions, valence fluctuations, and inter-ladder hopping.

Contribution

It provides a quantitative theoretical explanation of optical properties in $ ext{NaV}_2 ext{O}_5$ using a specific lattice model and explores the effects of valence fluctuations and inter-ladder hopping.

Findings

The t-J-V model explains the anisotropic optical conductivity.

Valence fluctuations cause domain wall excitations near criticality.

Inter-ladder hopping accounts for in-gap absorption and spectral weight at high energy.

Abstract

Using finite temperature diagonalization techniques it is shown that the quarter-filled t-J-V model on a trellis lattice structure provides a quantitative explanation of the highly anisotropic optical conductivity of the $\alpha'-NaV_{2}O_{5}$ compound. The combined effects of the short-range Coulomb interaction and valence fluctuations of V-ions determine the main absorption and the fundamental gap. Inter-ladder hopping is necessary for the explanation of the anomalous in-gap absorption and generation of spectral weight at high energy. The role of valence fluctuations is explained in terms of the domain wall excitations of an anisotropic 2D Ising model in a transverse field close to criticality.