Excitation Transport through a Domain Wall in a Bose-Einstein Condensate

TL;DR

This paper studies how collective excitations, like spin waves and Bogoliubov modes, interact with a domain wall in a spinor Bose-Einstein condensate, revealing unique reflection and transmission behaviors at different energies.

Contribution

It demonstrates the distinct tunneling properties of excitations through a domain wall in a spinor BEC, highlighting differences from classical ferromagnets and scalar condensates.

Findings

Transverse spin wave undergoes perfect reflection at low energy.

Bogoliubov mode shows non-monotonic transmission and reflection.

Perfect reflection occurs at energies where bound states form.

Abstract

We investigate the tunneling properties of collective excitations through a domain wall in the ferromagnetic phase of a spin-1 spinor Bose--Einstein condensate. Within the mean-field theory at T=0, we show that the transverse spin wave undergoes perfect reflection in the low-energy limit. This reflection property differs considerably from that of a domain wall in a Heisenberg ferromagnet where spin-wave excitations exhibit perfect transmission at arbitrary energy. When the Bogoliubov mode is scattered from this domain wall soliton, the transmission and reflection coefficients exhibit pronounced non-monotonicity. In particular, we find perfect reflection of the Bogoliubov mode at energies where bound states appear. This is in stark contrast to the perfect transmission of the Bogoliubov mode with arbitrary energy through a dark soliton in a scalar Bose--Einstein condensate.