Fingerprints of Universal Spin-Stiffness Jump in Two-Dimensional Ferromagnets

TL;DR

This paper proposes an experimental setup using spin-transport measurements to detect the universal spin-stiffness jump at the BKT transition in two-dimensional ferromagnets, enabling new insights into topological phase transitions.

Contribution

It introduces a novel experimental approach to observe the BKT transition via spin-current correlations in 2D magnetic systems.

Findings

Universal jump of 2/π in spin-stiffness can be measured.

Square root temperature dependence of spin-stiffness near transition.

Feasibility of detecting topological phase transition in 2D magnets.

Abstract

Motivated by recent progress on synthesizing two-dimensional magnetic van der Waals systems, we propose a setup for detecting the topological Berezinskii-Kosterlitz-Thouless (BKT) phase transition in spin-transport experiments on such structures. We demonstrate that the spatial correlations of injected spin-currents into a pair of metallic leads can be used to measure the predicted universal jump of $2/\pi$ in the ferromagnet spin-stiffness as well as its predicted universal square root dependence on temperature as the transition is approached from below. Our setup provides a simple route to measuring this topological phase transition in two-dimensional magnetic systems, something which up to now has proven elusive. It is hoped that this will encourage experimental efforts to investigate critical phenomena beyond the standard Ginzburg-Landau paradigm in low-dimensional magnetic systems with no local order parameter.