Identification of a Kitaev quantum spin liquid by magnetic field angle dependence

Kyusung Hwang,Takasada Shibauchi,Ara Go,Ji Heon Seong,Eun-Gook Moon

doi:10.1038/s41467-021-27943-9

Abstract

Quantum spin liquids realize massive entanglement and fractional quasiparticles from localized spins, proposed as an avenue for quantum science and technology. In particular, topological quantum computations are suggested in the non-abelian phase of Kitaev quantum spin liquid with Majorana fermions, and detection of Majorana fermions is one of the most outstanding problems in modern condensed matter physics. Here, we propose a concrete way to identify the non-abelian Kitaev quantum spin liquid by magnetic field angle dependence. Topologically protected critical lines exist on a plane of magnetic field angles, and their shapes are determined by microscopic spin interactions. A chirality operator plays a key role in demonstrating microscopic dependences of the critical lines. We also show that the chirality operator can be used to evaluate topological properties of the non-abelian Kitaev quantum spin liquid without relying on Majorana fermion descriptions. Experimental criteria for the non-abelian spin liquid state are provided for future experiments.

Highlights

Quantum spin liquids realize massive entanglement and fractional quasiparticles from localized spins, proposed as an avenue for quantum science and technology
The critical lines vary depending on the microscopic spin Hamiltonian, which we show by investigating a chirality operator via exact diagonalization
Intrinsic topological properties of the non-abelian KQSL including the critical lines, the symmetric zeroes, and the cubic dependence are highlighted in this work by exploiting the symmetries of time reversal and D3 point group

Summary

Introduction

Quantum spin liquids realize massive entanglement and fractional quasiparticles from localized spins, proposed as an avenue for quantum science and technology. We propose a concrete way to identify the non-abelian Kitaev quantum spin liquid by magnetic field angle dependence. We show that the chirality operator can be used to evaluate topological properties of the non-abelian Kitaev quantum spin liquid without relying on Majorana fermion descriptions. Thermal Hall measurements are known to be highly sensitive to sample qualities[64] and very challenging due to the required precision control of heat and magnetic torque from strong magnetic fields. This strongly motivates an independent way to detect the Majorana fermions and non-abelian KQSL. We further propose that the critical lines can be detected by heat capacity measurements and provide experimental criteria for the nonabelian KQSL applicable to the candidate material α-RuCl3

Methods

Results

Conclusion