Noise spectroscopy of unconventional spin transport phenomena in a two-dimensional Heisenberg ferromagnet

In recent studies, it has been demonstrated that spin transport coefficients in magnetic materials can be extracted through magnetic noise measurements of nearby spin qubits [1]. In this study, we placed nitrogen vacancy centers in close proximity to nanoflakes of CrCl3, a layered two-dimensional Heisenberg magnet, ranging from tens of layers to the monolayer limit. We are able to extract the spectral density of magnetic noise and imaginary susceptibility as functions of temperature and external magnetic field. Below the transition temperature, noise persists down to the lowest measurable temperature (5K), which can be explained by a model of a strongly interacting magnon gas where magnon-magnon collisions significantly influence the spin transport properties.

[1]Wang, Hailong, et al. "Noninvasive measurements of spin transport properties of an antiferromagnetic insulator." Science advances 8.1 (2022): eabg8562.