Probing thermal magnon current mediated by coherent magnon via nitrogen-vacancy centers in diamond

TL;DR

This paper demonstrates the detection of thermal magnon currents in yttrium iron garnet using nitrogen-vacancy centers in diamond, revealing a new quantum sensing approach for spin caloritronics.

Contribution

It introduces a novel method to detect thermal magnon currents via NV center spin states, bridging spin caloritronics and quantum sensing.

Findings

Thermal magnon currents modify NV Rabi oscillations.

NV spin relaxation rates depend on temperature gradients.

Long-distance propagation of coherent magnons was observed.

Abstract

Currently, thermally excited magnons are being intensively investigated owing to their potential in computing devices and thermoelectric conversion technologies. We report the detection of thermal magnon current propagating in a magnetic insulator yttrium iron garnet under a temperature gradient using a quantum sensor: electron spins associated with nitrogen-vacancy (NV) centers in diamond. Thermal magnon current was observed as modified Rabi oscillation frequencies of NV spins hosted in a beam-shaped bulk diamond that resonantly coupled with coherent magnon propagating over a long distance. Additionally, using a nanodiamond, alteration in NV spin relaxation rates depending on the applied temperature gradient were observed under a non-resonant NV excitation condition. The demonstration of probing thermal magnon current mediated by coherent magnon via NV spin states serves as a basis for creating a device platform hybridizing spin caloritronics and spin qubits.