High-temperature optical spectral weight and Fermi liquid renormalization in Bi-based cuprates

TL;DR

This study investigates the optical spectral weight and Fermi liquid behavior in Bi-based cuprates at high temperatures, revealing strong correlation effects and deviations from conventional T2 behavior, supported by experimental and theoretical analysis.

Contribution

It provides the first high-temperature measurements of spectral weight in Bi-based cuprates and links deviations to strong correlation effects using dynamical mean field theory.

Findings

Spectral weight deviates from T2 behavior above 300 K.

Deviations are well described by T4 term of Sommerfeld expansion.

Strong correlations enhance the coefficients of the T4 term.

Abstract

The optical conductivity and the spectral weight W(T) of two superconducting cuprates at optimum doping, Bi2Sr2-xLaxCuO6 and Bi2Sr2CaCu2O8, have been first measured up to 500 K. Above 300 K, W(T) deviates from the usual T2 behavior in both compounds, even though the zero-frequency extrapolation of the optical conductivity remains larger than the Ioffe-Regel limit. The deviation is surprisingly well described by the T4 term of the Sommerfeld expansion, but its coefficients are enhanced by strong correlation. This renormalization is due to strong correlation, as shown by the good agreement with dynamical mean field calculations.