Nanophotonic structures with optical surface modes for tunable spin current generation

TL;DR

This paper introduces a novel photonic-crystal structure that enhances and tunes optically-induced spin current generation using surface modes, achieving high efficiency even with ultra-thin layers and enabling localized spin current control.

Contribution

The work demonstrates a new PC-based design for efficient, tunable spin current generation via optical surface modes, surpassing traditional methods in efficiency and scalability.

Findings

Optical surface modes significantly increase spin current efficiency.

Up to 100% of incident light power can be converted to heat and spin current.

Surface patterning enables local spin current generation at small scales.

Abstract

Heat generated by spin currents in spintronics-based devices is typically much less than that generated by charge current flows in conventional electronic devices. However, the conventional approaches for excitation of spin currents based on spin-pumping and spin Hall effect are limited in efficiency which restricts their application for viable spintronic devices. We propose a novel type of photonic-crystal (PC) based structures for efficient and tunable optically-induced spin current generation via the Spin Seebeck and inverse spin Hall effects. It is experimentally demonstrated that optical surface modes localized at the PC surface covered by ferromagnetic layer and materials with giant spin-orbit coupling (SOC) notably increase the efficiency of the optically-induced spin current generation and provides its tunability by modifying light wavelength or angle of incidence. Up to 100% of the incident light power can be transferred to heat within the SOC layer and, therefore, to spin current. Importantly, high efficiency becomes accessible even for ultra-thin SOC layers. Moreover, surface patterning of the PC-based spintronic nanostructure allows local generation of spin currents at the pattern scales rather than diameter of the laser beam.