Emergence of Chiral Magnetism in Spinor Bose-Einstein Condensate with Rashba Coupling

TL;DR

This paper develops a hydrodynamic theory for spinor Bose-Einstein condensates with Rashba spin-orbit coupling, revealing a mathematical analogy to chiral magnetism and analyzing elementary excitations in different ground states.

Contribution

It introduces a hydrodynamic framework for Rashba-coupled spinor BECs, highlighting the emergence of chiral magnetism-like behavior and deriving excitation spectra.

Findings

Mass current includes an extra term due to Rashba coupling.

Elementary excitations show spin-superflow cross-coupling.

Analogy between Rashba-BEC and chiral magnetism established.

Abstract

Hydrodynamic theory of the spinor BEC condensate with Rashba spin-orbit coupling is presented. A close mathematical analogy of the Rashba-BEC model to the recently developed theory of chiral magnetism is found. Hydrodynamic equations for mass density, superfluid velocity, and the local magnetization are derived. The mass current is shown to contain an extra term proportional to the magnetization direction, as a result of the Rashba coupling. Elementary excitations around the two known ground states of the Rashba-BEC Hamiltonian, the plane-wave and the stripe states, are worked out in the hydrodynamic framework, highlighting the cross-coupling of spin and superflow velocity excitations due to the Rashba term.