Strain Response as a Probe of Spinons in Quantum Spin Liquids

TL;DR

This paper proposes using lattice strain as a novel, tunable method to detect and distinguish different quantum spin liquid phases by inducing pseudomagnetic fields and observing their unique spectroscopic signatures.

Contribution

It introduces a new strain-based probe for identifying fractionalized excitations in quantum spin liquids, supported by theoretical analysis of the Kitaev model.

Findings

Distinct QSL phases show different strain responses.

Landau quantization appears in certain QSL phases under strain.

Local ultrasound spectroscopy can detect strain-induced resonances.

Abstract

Quantum spin liquids (QSLs) host emergent, fractionalized fermionic excitations that are charge-neutral. Identifying clear experimental signatures of these excitations remains a central challenge in the field of strongly correlated systems, as they do not couple to conventional electromagnetic probes. Here, we propose lattice strain as a powerful and tunable probe: Mechanical deformation of the lattice generates large pseudomagnetic fields, inducing pseudo-Landau levels that serve as distinctive spectroscopic signatures of these excitations. Using the Kitaev model on the honeycomb lattice, we show that distinct QSL phases exhibit strikingly different strain responses. The semimetallic Kitaev spin liquid and the gapped chiral spin liquid display pronounced Landau quantization and a diamagnetic-like response to strain, whereas the Majorana metal phase shows a paramagnetic-like response without forming Landau levels. These contrasting behaviors provide a direct route to experimentally identifying and distinguishing QSL phases hosting fractionalized excitations. We further outline how local resonant ultrasound spectroscopy can detect the strain-induced resonances associated with these responses, offering a practical pathway towards identifying fractionalized excitations in candidate materials.