Triggering phase-coherent spin packets by pulsed electrical spin injection across an Fe/GaAs Schottky barrier

TL;DR

This paper demonstrates a method to generate and control phase-coherent spin packets in a semiconductor using pulsed electrical injection across an Fe/GaAs Schottky barrier, enabling microwave-frequency spin manipulation.

Contribution

It introduces a pulsed electrical scheme for initializing phase-coherent spin packets in semiconductor spintronics, comparable to optical methods, with high-frequency control capabilities.

Findings

Phase coherence observed for current pulses as short as 500 ps.

Spin coherence limited by Schottky barrier charging times and pulse bandwidth.

All-electrical spin injection and phase control achieved at microwave frequencies.

Abstract

The precise control of spins in semiconductor spintronic devices requires electrical means for generating spin packets with a well-defined initial phase. We demonstrate a pulsed electrical scheme that triggers the spin ensemble phase in a similar way as circularly-polarized optical pulses are generating phase coherent spin packets. Here, we use fast current pulses to initialize phase coherent spin packets, which are injected across an Fe/GaAs Schottky barrier into $n$-GaAs. By means of time-resolved Faraday rotation, we demonstrate phase coherence by the observation of multiple Larmor precession cycles for current pulse widths down to 500 ps at 17 K. We show that the current pulses are broadened by the charging and discharging time of the Schottky barrier. At high frequencies, the observable spin coherence is limited only by the finite band width of the current pulses, which is on the order of 2 GHz. These results therefore demonstrate that all-electrical injection and phase control of electron spin packets at microwave frequencies is possible in metallic-ferromagnet/semiconductor heterostructures.