Optical Sum Rule anomalies in the High-Tc Cuprates

TL;DR

This paper reviews sum rule anomalies in high-Tc cuprates, highlighting the effects of finite frequency cutoffs and confirming the persistent spectral weight increase below the superconducting transition.

Contribution

It clarifies the impact of finite cutoff frequencies on sum rule measurements and confirms the robustness of the spectral weight anomaly in the superconducting state.

Findings

Normal state sum rule anomalies explained by cutoff effects

Persistent spectral weight increase below Tc confirmed

Finite cutoff frequency influences experimental observations

Abstract

We provide a brief summary of the observed sum rule anomalies in the high-T$_c$ cuprate materials. A recent issue has been the impact of a non-infinite frequency cutoff in the experiment. In the normal state, the observed anomalously high temperature dependence can be explained as a `cutoff effect'. The anomalous rise in the optical spectral weight below the superconducting transition, however, remains as a solid experimental observation, even with the use of a cutoff frequency.