Ballistic Spin Resonance

TL;DR

This paper reports the discovery of ballistic spin resonance (BSR), a new type of spin resonance driven by internal spin-orbit fields in ultra-clean 2DEG channels, enabling gate-tunable spin control without external fields.

Contribution

It introduces BSR as a novel resonance phenomenon caused by internal SOI, expanding understanding of spin dynamics in ballistic nanostructures.

Findings

BSR causes strong suppression of spin relaxation length.

Resonance occurs at gigaHertz frequencies in narrow channels.

Electrical measurements reveal pure spin current modulation.

Abstract

The phenomenon of spin resonance has had far reaching influence since its discovery nearly 70 years ago. Electron spin resonance (ESR) driven by high frequency magnetic fields has informed our understanding of quantum mechanics, and finds application in fields as diverse as medicine and quantum information. Spin resonance induced by high frequency electric fields, known as electric dipole spin resonance (EDSR), has also been demonstrated recently. EDSR is mediated by spin-orbit interaction (SOI), which couples the spin degree of freedom and the momentum vector. Here, we report the observation of a novel spin resonance due to SOI that does not require external driving fields. Ballistic spin resonance (BSR) is driven by an internal spin-orbit field that acts upon electrons bouncing at gigaHertz frequencies in narrow channels of ultra-clean two-dimensional electron gas (2DEG). BSR is manifested in electrical measurements of pure spin currents as a strong suppression of spin relaxation length when the motion of electrons is in resonance with spin precession. These findings point the way to gate-tunable coherent spin rotations in ballistic nanostructures without external a.c. fields.