Driving a pure spin current from nuclear-polarization gradients

TL;DR

This paper predicts a novel method to generate a pure spin current using nuclear-polarization gradients and specific magnetic field alignments, supported by a classical model and proposed experimental verification.

Contribution

It introduces a new theoretical mechanism for pure spin current generation based on nuclear hyperfine fields and spin-dependent dispersion in free electrons.

Findings

Prediction of pure spin current from nuclear-polarization gradients.

Identification of conditions for spin-dependent dispersion.

Proposal of optical and electrical experiments for validation.

Abstract

A pure spin current is predicted to occur when an external magnetic field and a linearly inhomogeneous spin-only field are appropriately aligned. Under these conditions (such as originate from nuclear contact hyperfine fields that do not affect orbital motion) a linear, spin-dependent dispersion for free electrons emerges from the Landau Hamiltonian. The result is that spins of opposite orientation flow in opposite directions giving rise to a pure spin current. A classical model of the spin and charge dynamics reveals intuitive aspects of the full quantum mechanical solution. We propose optical orientation or electrical polarization experiments to demonstrate this outcome.