Optical conductivity of doped Mott insulator: the interplay between correlation and electron-phonon interaction

TL;DR

This paper presents a theoretical study of the optical conductivity in doped cuprates using an advanced numerical method, revealing detailed features of the mid-infrared spectrum and clarifying the origins of observed peaks.

Contribution

The study introduces the LPBED method to analyze the t-t'-J-Holstein model, providing new insights into the MIR peaks' magnetic and phononic origins in doped Mott insulators.

Findings

Identification of a three-peak structure in the MIR optical conductivity.

The lowest MIR peak is mainly due to hole-phonon scattering.

The middle MIR peak has a magnetic origin.

Abstract

The optical conductivity (OC) of cuprates is studied theoretically in the low density limit of the t-t'-J-Holstein model. By developing a limited phonon basis exact diagonalization (LPBED) method capable of treating the lattice of largest size 4x4 ever considered, we are able to discern fine features of the mid-infrared (MIR) part of the OC revealing three-peak structure. The two lowest peaks are observed in experiments and the highest one is tacitly resolved in moderately doped cuprates. Comparison of OC with the results of semianalytic approaches and detailed analysis of the calculated isotope effect indicate that the middle-energy MIR peak is of mostly magnetic origin while the lowest MIR band originates from the scattering of holes by phonons.