Maxwell Equation for the Coupled Spin-Charge Wave Propagation

TL;DR

This paper demonstrates a Maxwell-like coupling between spin and charge waves in a Rashba system, predicting spontaneous splitting of density packets and proposing experiments for detection.

Contribution

It introduces a novel Maxwell-equation analogy for spin-charge coupling in the Rashba model, revealing new wave propagation phenomena.

Findings

Density packets can split into counter-propagating spin-carrying packets.

Coupled spin-charge waves can propagate like transverse photons.

Proposed experiments to observe these effects.

Abstract

We show that the dissipationless spin current in the ground state of the Rashba model gives rise to a reactive coupling between the spin and charge propagation, which is formally identical to the coupling between the electric and the magnetic fields in the 2+1 dimensional Maxwell equation. This analogy leads to a remarkable prediction that a density packet can spontaneously split into two counter propagation packets, each carrying the opposite spins. In a certain parameter regime, the coupled spin and charge wave propagates like a transverse "photon". We propose both optical and purely electronic experiments to detect this effect.