Controlling encirclement of an exceptional point using coupled spintronic nano-oscillators

TL;DR

This paper demonstrates control and topological manipulation of exceptional points in coupled spintronic nano-oscillators, revealing their potential for exploring non-Hermitian physics at room temperature.

Contribution

It introduces a novel method to control and encircle exceptional points in spintronic systems by tuning damping and phase, highlighting their topological properties.

Findings

Control over level attraction and repulsion near EPs

Successful topological encircling of EPs causing eigenstate switching

Experimental validation at room temperature

Abstract

Exceptional points (EPs), branch singularities parameter space of non-Hermitian eigenvalue manifolds, display unique topological phenomena linked to eigenvalue and eigenvector switching: the parameter space states are highly sensitive to the system's parameter changes. Therefore, we suggest investigating the parameter space in the presence of an EP by experimentally accessing and exploiting the topological nature of the coupled system around an EP. We demonstrate control over exceptional points in coupled vortex spin-transfer torque oscillators by adjusting the system's damping through the spin-transfer torque effect and their relative phase. This approach allows for precise manipulation of the coupling behavior in the vicinity of an exceptional point. We report the presence of both level attraction/repulsion by adjusting the system's parameters. Moreover, we evidence the topological nature of the EP by dynamically encircling it in the phase-current parameter space, leading to a switch of the eigenstates. Our study introduces a new method for exploring non-Hermitian physics in spintronic systems at room temperature.