Heavy fermion spin liquid in herbertsmithite

TL;DR

This paper demonstrates that herbertsmithite exhibits a stable quantum spin liquid state with properties similar to heavy fermion metals, showing no gap in spinon excitations even under high magnetic fields.

Contribution

It provides evidence that herbertsmithite hosts a strongly correlated quantum spin liquid with heavy fermion-like behavior, extending understanding of quantum spin liquids in magnetic materials.

Findings

Spinon effective mass scales with magnetic field similar to heavy fermion systems.

Heat capacity measurements are consistent across single crystal and powder samples.

No gap in spinon excitation spectra observed up to 18 T magnetic field.

Abstract

We analyze recent heat capacity measurements in herbertsmithite $\rm ZnCu_3(OH)_6Cl_2$ single crystal samples subjected to strong magnetic fields. We show that the temperature dependence of specific heat $C_{mag}$ formed by quantum spin liquid at different magnetic fields $B$ resembles the electronic heat capacity $C_{el}$ of the HF metal $\rm YbRh_2Si_2$. We demonstrate that the spinon effective mass $M^*_{mag}\propto C_{mag}/T$ exhibits a scaling behavior like that of $C_{el}/T$. We also show that the recent measurements of $C_{mag}$ are compatible with those obtained on powder samples. These observations allow us to conclude that $\rm ZnCu_3(OH)_6Cl_2$ holds a stable strongly correlated quantum spin liquid, and a possible gap in the spectra of spinon excitations is absent even under the application of very high magnetic fields of 18 T.