Detecting End-States of Topological Quantum Paramagnets via Spin Hall Noise Spectroscopy

TL;DR

This paper proposes using inverse spin Hall effect-based spin noise spectroscopy to detect topological phase transitions in quantum paramagnets, providing a new experimental tool for identifying topological states.

Contribution

It introduces a theoretical framework for using spin noise measurements via ISHE to identify topological phases in quantum spin systems, especially in quantum spin ladders.

Findings

Charge noise spectra reveal boundary spin correlations.

Spin noise spectroscopy can detect topological phase transitions.

Method applicable to various quantum paramagnets.

Abstract

We theoretically study the equilibrium spin current fluctuations and the corresponding charge noise generated by inverse spin Hall effect (ISHE) in a metal with strong spin-orbit coupling deposited on top of a quantum paramagnet. It is shown that the charge noise power spectra measured along different spatial axes can directly probe the different spin components of the boundary dynamic spin correlations of the quantum paramagnet. We report the utility of this ISHE-facilitated spin noise probe as a tool to unambiguously detect topological phase transitions in an S=1/2 quantum spin ladder that hosts a trivial ground state of singlet product states, but topologically-protected fractional spin excitations localized at its ends. Our work demonstrates the general usefulness of the ISHE-mediated spin noise spectroscopy for the detection of topological phases in quantum paramagnets.