Crossover from weak to strong quench in a spinor Bose-Einstein condensate

TL;DR

This paper studies the early-time dynamics of a quasi-two-dimensional spin-1 antiferromagnetic Bose-Einstein condensate after a sudden quench, revealing a crossover from long-wavelength to suppressed spin excitations as quench strength increases.

Contribution

It demonstrates the crossover behavior in spin excitation dynamics post-quench and links it to the Bogoliubov theory of dynamic instability in spinor condensates.

Findings

Long-wavelength spin excitations dominate for weak quenches.

High quench strength suppresses long-wavelength instabilities.

Crossover behavior aligns with Bogoliubov theory predictions.

Abstract

We investigate the early-time dynamics of a quasi-two-dimensional spin-1 antiferromagnetic Bose-Einstein condensate after a sudden quench from the easy-plane to the easy-axis polar phase. The post-quench dynamics shows a crossover behavior as the quench strength $\tilde{q}$ is increased, where $\tilde{q}$ is defined as the ratio of the initial excitation energy per particle to the characteristic spin interaction energy. For a weak quench of $\tilde{q}<1$, long-wavelength spin excitations are dominantly generated, leading to the formation of irregular spin domains. With increasing $\tilde{q}$, the length scale of the initial spin excitations decreases, and we demonstrate that the long-wavelength instability is strongly suppressed for high $\tilde{q}>2$. The observed crossover behavior is found to be consistent with the Bogoliubov description of the dynamic instability of the initial spinor condensate.