Diagnosing phases of magnetic insulators via noise magnetometry with spin qubits

TL;DR

This paper proposes using noise magnetometry with spin qubits to diagnose and distinguish various magnetic ground states in two-dimensional magnetic insulators by measuring spin correlations with high energy and wavevector resolution.

Contribution

It introduces a method employing tunable spin qubits as probes to identify different magnetic phases and excitations in insulators, including quantum spin liquids and topological states.

Findings

Spin qubits can detect fractionalized excitations in spin liquids.

The method distinguishes between spin waves and fractionalized particles.

It enables measurement of spin correlations with energy and wavevector resolution.

Abstract

Two-dimensional magnetic insulators exhibit a plethora of competing ground states, such as ordered (anti)ferromagnets, exotic quantum spin liquid states with topological order and anyonic excitations, and random singlet phases emerging in highly disordered frustrated magnets. Here we show how single spin qubits, which interact directly with the low-energy excitations of magnetic insulators, can be used as a diagnostic of magnetic ground states. Experimentally tunable parameters, such as qubit level splitting, sample temperature, and qubit-sample distance, can be used to measure spin correlations with energy and wavevector resolution. Such resolution can be exploited, for instance, to distinguish between fractionalized excitations in spin liquids and spin waves in magnetically ordered states, or to detect anyonic statistics in gapped systems.