Optical Conductivity of the Trellis-Lattice t-J Model: Charge Fluctuations in NaV_2O_5

TL;DR

This paper calculates the optical conductivity of the trellis-lattice t-J model for NaV_2O_5, demonstrating that charge disproportionation explains experimental spectral features, with implications for understanding charge order.

Contribution

It provides the first theoretical calculation of optical conductivity for the trellis-lattice t-J model considering charge disproportionation, aligning with experimental observations.

Findings

Reproduces experimental spectral features at ~1 eV

Shows charge disproportionation is necessary for observed spectra

Discusses possible coexistence of uniform ladders above T_c

Abstract

Optical conductivity of the trellis lattice t-J model at quarter filling is calculated by an exact-diagonalization technique on small clusters, whereby the valence state of V ions of NaV_2O_5 is considered. We show that the experimental features at \sim 1 eV, including peak positions, presence of shoulders, and anisotropic spectral weight, can be reproduced in reasonable range of parameter values, only by assuming that the system is in the charge disproportionated ground state. Possible reconciliation with experimental data suggesting the presence of uniform ladders at T>T_c is discussed.