Optical Conductivity of a t--J Ladder

TL;DR

This paper calculates the optical conductivity of a doped two-leg t--J ladder, revealing a doping-dependent Drude weight and a pseudogap linked to pair-breaking energy, influenced by ladder geometry.

Contribution

It provides the first detailed analysis of optical conductivity in a doped t--J ladder, highlighting the pseudogap and its relation to pairing and geometry.

Findings

Drude weight proportional to hole doping

Presence of a pseudogap in optical conductivity

Pseudogap associated with pair-breaking energy

Abstract

The optical conductivity $\sigma(\omega )$ of a doped two-leg t--J ladder is calculated for an electric field polarized parallel to the legs of the ladder. The conductivity has a Drude weight proportional to the hole doping and an apparent threshold for absorption (a pseudo gap) which may be associated with the energy to break a pair. This pseudogap in $\sigma (\omega )$ is present even though the pairs have a modified $d_{x^2-y^2}$-like wave function because the geometry of the ladder leads to quasi-particle states which probe the gap along an antinode.