Optical conductivity and surface plasmon modes of U(1) spin liquid states with large spinon Fermi surfaces

TL;DR

This paper investigates the optical properties of U(1) spin liquids with large spinon Fermi surfaces, revealing a unique optical conductivity feature and a detectable surface plasmon mode above the charge gap.

Contribution

It introduces a simple formula for the bulk optical conductivity of U(1) spin liquids and predicts a long-lived surface plasmon mode at the interface, distinguishable from ordinary insulators.

Findings

Distinct optical conductivity above the charge gap

Existence of a long-lived surface plasmon mode

Detectability via Kretschmann-Raether configuration

Abstract

In this paper we study the optical properties of $U(1)$ spin liquids with large spinon Fermi surfaces based on a simple formula for the bulk optical conductivity obtained through the Ioffe-Larkin composition rule. We show that the optical conductivity of $U(1)$ spin liquids at energies above the charge gap has a unique feature that distinguishes them from ordinary insulators. In particular we show the existence of a long-life surface plasmon mode propagating along the interface between a linear medium and the spin liquid at frequencies above the charge gap, which can be detected by the widely used Kretschmann-Raether three-layer configuration.