Time-resolved lateral spin-caloric transport of optically generated spin packets in n-GaAs

TL;DR

This study investigates how optically generated electron spin packets in n-GaAs move laterally under a temperature gradient at low temperatures, revealing non-classical diffusion driven by hot spin distributions without phonon drag effects.

Contribution

It demonstrates the lateral spin-caloric transport driven by temperature gradients and verifies the non-classical Einstein relation in n-GaAs at low temperatures.

Findings

Spin packets exhibit lateral transport driven by temperature gradients.

Transport is due to hot spin distributions, not phonon drag.

Non-classical Einstein relation is validated for n-GaAs.

Abstract

We report on lateral spin-caloric transport (LSCT) of electron spin packets which are optically generated by ps laser pulses in the non-magnetic semiconductor n-GaAs at $T\leq35$K. LSCT is driven by a local temperature gradient induced by an additional cw heating laser. The spatio-temporal evolution of the spin packets is probed using time-resolved Faraday rotation. We demonstrate that the local temperature-gradient induced spin diffusion is solely driven by a non-equilibrium hot spin distribution, i.e. without involvement of phonon drag effects. Additional electric field-driven spin drift experiments are used to verify directly the validity of the non-classical Einstein relation for moderately doped semiconductors at low temperatures for near band-gap excitation.