Universal behavior of quantum spin liquid and optical conductivity in the insulator herbertsmithite

TL;DR

This paper investigates the optical conductivity of herbertsmithite, providing experimental evidence for a quantum spin liquid state with fermion condensate characteristics and predicting its response to magnetic fields.

Contribution

The study models the quantum spin liquid near fermion condensation transition, explaining temperature dependence and predicting magnetic field effects on optical conductivity.

Findings

Optical conductivity exhibits temperature dependence consistent with fermion condensate behavior.

Theoretical model explains the physical mechanism behind temperature effects.

Predicted magnetic field dependence of optical conductivity in herbertsmithite.

Abstract

We analyze optical conductivity with the goal to demonstrate experimental manifestation of a new state of matter, the so-called fermion condensate. Fermion condensates are realized in quantum spin liquids, exhibiting typical behavior of heavy fermion metals. Measurements of the low-frequency optical conductivity collected on the geometrically frustrated insulator herbertsmithite provide important experimental evidence of the nature of its quantum spin liquid composed of spinons. To analyze recent measurements of the herbertsmithite optical conductivity at different temperatures, we employ a model of strongly correlated quantum spin liquid located near the fermion condensation phase transition. Our theoretical analysis of the optical conductivity allows us to expose the physical mechanism of its temperature dependence. We also predict a dependence of the optical conductivity on a magnetic field. We consider an experimental manifestation (optical conductivity) of a new state of matter (so-called fermion condensate) realized in quantum spin liquids, for, in many ways, they exhibit typical behavior of heavy-fermion metals. Measurements of the low-frequency optical conductivity collected on the geometrically frustrated insulator herbertsmithite produce important experimental evidence of the nature of its quantum spin liquid composed of spinons. To analyze recent measurements of the herbertsmithite optical conductivity at different temperatures, we employ a model of strongly correlated quantum spin liquid located near the fermion condensation phase transition. Our theoretical analysis of the optical conductivity allows us to reveal the physical mechanism of its temperature dependence. We also predict a dependence of the optical conductivity on a magnetic field.