Transient spin current under a thermal switch

TL;DR

This paper presents a theoretical study on transient spin currents induced by thermal switching, showing significant ultrafast enhancement and spatial variation, with potential applications in spintronics.

Contribution

It provides a closed-form solution for transient spin current in nonlinear quantum transport and demonstrates ultrafast enhancement via thermal switches.

Findings

Transient spin current can vary spatially, causing spin accumulation or depletion.

Transient spin current can increase by 2-3 orders of magnitude compared to steady state.

Ultrafast enhancement of spin currents is achievable through thermal switching.

Abstract

In this work, we explore the possibility of enhancing a spin current under a thermal switch, i.e., connecting the central transport region to two leads in individual thermal equilibrium abruptly. Using the nonequilibrium Green's function method for the transient spin current, we obtain a closed-form solution, which is applicable in the whole nonlinear quantum transport regime with a significant reduction of computational complexity. Furthermore, we perform a model calculation on a single-level quantum dot with Lorentzian linewidth. It shows that the transient spin current may vary spatially, causing spin accumulation or depletion in the central region. Moreover, general enhancement of the spin current in the transient regime is observed. In particular, the in-plane components of the transient spin current may increase by 2-3 orders of magnitude compared to the steady-state thermoelectric spin current under a temperature difference of 30 K. Our research demonstrates that ultrafast enhancement of spin currents can be effectively achieved by thermal switches.