Crossover from Diffusive to Superfluid Transport in Frustrated Magnets

TL;DR

This paper explores how spin transport in frustrated antiferromagnetic insulators transitions from diffusive to superfluid behavior, depending on magnetic configurations and frustration levels, revealing robustness near phase boundaries.

Contribution

It demonstrates the crossover from diffusive to superfluid spin transport in a frustrated magnet using atomistic simulations across the phase diagram.

Findings

Spin superfluidity persists when magnetic moments are in-plane.

Frustration and out-of-plane canting lead to diffusive transport.

Proximate spin superfluidity exists near ferromagnetic transitions.

Abstract

We investigate the spin transport across the magnetic phase diagram of a frustrated antiferromagnetic insulator and uncover a drastic modification of the transport regime from spin diffusion to spin superfluidity. Adopting a triangular lattice accounting for both nearest neighbor and next-nearest neighbor exchange interactions with easy-plane anisotropy, we perform atomistic spin simulations on a two-terminal configuration across the full magnetic phase diagram. We found that as long as the ground state magnetic moments remain in-plane, irrespective of whether the magnetic configuration is ferromagnetic, collinear or non-collinear antiferromagnetic, the system exhibits spin superfluid behavior with a device output that is independent on the value of the exchange interactions. When the magnetic frustration is large enough to compete with the easy-plane anisotropy and cant the magnetic moments out of the plane, the spin transport progressively evolves towards the diffusive regime. The robustness of spin superfluidity close to magnetic phase boundaries is investigated and we uncover the possibility for {\em proximate} spin superfluidity close to the ferromagnetic transition.