Non-hermiticity in spintronics: oscillation death in coupled spintronic nano-oscillators through emerging exceptional points

Authors: Steffen Wittrock, Salvatore Perna, Romain Lebrun, Roberta Dutra, Ricardo Ferreira, Paolo Bortolotti, Claudio Serpico, Vincent Cros,

The emergence of exceptional points (EPs) in the parameter space of a non-hermitian
(2D) eigenvalue problem is studied in a general sense in mathematical physics, and has
in the last decade successively reached the scope of experiments. In coupled systems,
it gives rise to unique physical phenomena, which enable novel approaches for the de-
velopment of seminal types of highly sensitive sensors. Here, we demonstrate at room
temperature the emergence of EPs in coupled spintronic nanoscale oscillators and hence
exploit the system’s non-hermiticity. We describe the observation of amplitude death
of self-oscillations and other complex dynamics, and develop a linearized non-hermitian
model of the coupled spintronic system, which properly describes the main experimen-
tal features. Interestingly, these spintronic nanoscale oscillators are deployment-ready
in different applicational technologies, such as field, current or rotation sensors, ra-
diofrequeny and wireless devices and, more recently, novel neuromorphic hardware
solutions. Their unique and versatile properties, notably their large nonlinear behav-
ior, open up unprecedented perspectives in experiments as well as in theory on the
physics of exceptional points. Furthermore, the exploitation of EPs in spintronics de-
vises a new paradigm for ultrasensitive nanoscale sensors and the implementation of
complex dynamics in the framework of non-conventional computing.