Easy-plane spin Hall nano-oscillators as spiking neurons for neuromorphic computing

Abstract

We show analytically using a macrospin approximation that easy-plane spin Hall nano-oscillators excited by a spin-current polarized perpendicularly to the easy-plane have phase dynamics analogous to that of Josephson junctions. Similarly to Josephson junctions, they can reproduce the spiking behavior of biological neurons that is appropriate for neuromorphic computing. We perform micromagnetic simulations of such oscillators realized in the nano-constriction geometry and show that the easy-plane spiking dynamics is preserved in an experimentally feasible architecture. Finally we simulate two elementary neural network blocks that implement operations essential for neuromorphic computing. First, we show that output spikes energies from two neurons can be summed and injected into a following layer neuron and second, we demonstrate that outputs can be multiplied by synaptic weights implemented by locally modifying the anisotropy.

Quantum materials for energy-efficient neuromorphic computing

“…For this, antiferromagnets as well as synthetic antiferromagnets are promising due to their terahertz speed and spiking ability. 129,130 While new materials could provide efficient generation of magnetization dynamics as the basis for neuromorphic computing using spin oscillators, 21,27,131,132 they do not address adjusting synaptic weights or enabling high connectivity between individual oscillators. A neuromorphic circuit requires the output of a neuron to serve as the input to other neurons with learning associated with adjustment of the "synaptic" weights of the inputs to the neurons.…”

“…Recently, a ferromagnetic structure that gives similar behavior in ferromagnetic systems was proposed. 130 These proposals are theoretical for now and demonstrating them experimentally is an important challenge for future spintronic neuromorphic systems.…”