Non-reciprocal spin excitations across the skyrmion-paramagnetic phase transition in MnSi

TL;DR

This study investigates the evolution of non-reciprocal spin excitations in MnSi across the skyrmion-paramagnetic phase transition, revealing persistent non-reciprocal behavior above the critical temperature.

Contribution

It provides experimental evidence of non-reciprocal spin excitations persisting beyond the skyrmion phase, supported by neutron scattering and linear spin-wave theory.

Findings

Non-reciprocal excitations persist above the skyrmion phase.

Excitations vary smoothly across the phase boundary.

Results are consistent with linear spin-wave theory.

Abstract

The magnetic excitations of the skyrmion lattice in MnSi comprise a multitude of individual modes, which are non-reciprocal and thereby propagate unidirectionally. We report inelastic neutron scattering experiments for temperatures near and above the skyrmion-paramagnetic phase transition in the chiral magnet MnSi tracking the evolution from the skyrmion lattice towards the high-temperature paramagnetic state. Within the resolution of the triple-axis measurements the excitations vary smoothly across the skyrmion-paramagnetic boundary, and, the quasi-elastic paramagnetic signal under applied field retains the non-reciprocal character seen in the skyrmion phase even far above the critical temperature. Using a resolution-convolution our results are consistent with linear spin-wave theory.