Power dependence of pure spin current injection by quantum interference

TL;DR

This study explores how the injection of pure spin currents in GaAs materials depends on laser power, demonstrating a monotonic increase in spin current density with laser intensity, supported by experimental and theoretical analysis.

Contribution

It provides new insights into the power dependence of pure spin current injection using quantum interference control in GaAs.

Findings

Spin separation relates to the relative strength of transition pathways.

Injected spin current density increases monotonically with laser intensity.

Experimental results align with Fermi's golden rule calculations.

Abstract

We investigate the power dependence of pure spin current injection in GaAs bulk and quantum-well samples by a quantum interference and control technique. Spin separation is measured as a function of the relative strength of the two transition pathways driven by two laser pulses. By keeping the relaxation time of the current unchanged, we are able to relate the spin separation to the injected average velocity. We find that the average velocity is determined by the relative strength of the two transitions in the same way as in classical interference. Based on this, we conclude that the density of injected pure spin current increases monotonically with the excitation laser intensities. The experimental results are consistent with theoretical calculations based on Fermi's golden rule.