The Pseudogap Challenge: Understanding the ab-Plane AC Conductivity below Tc

TL;DR

This paper investigates how the pseudogap influences the ab-plane optical conductivity in cuprates below the critical temperature, distinguishing between competing theories based on their spectral signatures and temperature dependence.

Contribution

It provides a comparative analysis of pseudogap models, highlighting their distinct optical conductivity signatures and implications for understanding cuprate superconductivity.

Findings

Distinct $ ext{ω}$ and $T$ dependences for competing pseudogap models.

Excess low-frequency spectral weight increases with temperature in the superconducting scenario.

Wider spectral range contributes to condensate formation in the superconducting case.

Abstract

We establish that the cuprate pseudogap plays a crucial role in the $ab$-plane optical conductivity $\sigma(\omega,T)$ for temperatures $T \le T_c$. The pseudogap signatures in $\sigma(\omega,T)$ associated with competing proposals of a ``hidden order'' and ``superconducting'' origin for the $d_{x^2 - y^2}$ pseudogap are found to differ in their qualitative $\omega,T$ dependences. For the latter case, as $T$ increases from 0, excess low $\omega$ weight appears; moreover, a much wider range of $\omega$ contributes to form the condensate. We discuss these theories in light of current experiments.