Solitons and Josephson-type oscillations in Bose-Einstein condensates with spin-orbit coupling and time-varying Raman frequency

TL;DR

This paper explores how solitons in spin-orbit coupled Bose-Einstein condensates can be manipulated using time-varying Raman frequencies, revealing mechanisms for converting soliton types and controlling their dynamics through parametric resonances.

Contribution

It introduces a method to control soliton properties in BECs with SOC via time-dependent Raman frequencies, including soliton conversion and resonance-based parameter tuning.

Findings

Raman frequency variation enables conversion between bright and striped solitons.

Parametric resonances can control soliton parameters.

Numerical simulations confirm the variational analysis predictions.

Abstract

The existence and dynamics of solitons in quasi-one-dimensional Bose-Einstein condensates (BEC) with spin-orbit coupling (SOC) and attractive two-body interactions are described for two coupled atomic pseudo-spin components with slowly and rapidly varying time-dependent Raman frequency. By varying the Raman frequency linearly in time, it was shown that ordinary nonlinear Schr\"odinger-type bright solitons can be converted to striped bright solitons and vice versa. The internal Josephson oscillations between atom-number of the coupled soliton components, and the corresponding center-of-mass motion, are studied for different parameter configurations. In this case, a mechanism to control the soliton parameters is proposed by considering parametric resonances, which can emerge when using time-varying Raman frequencies. Full numerical simulations confirm variational analysis predictions when applied to the region where regular solitons are expected. In the limit of high frequencies, the system is described by a time-averaged Gross-Pitaevskii formalism with renormalized nonlinear and SOC parameters and modified phase-dependent nonlinearities. By comparing full-numerical simulations with averaged results, we have also studied the lower limits for the frequency of Raman oscillations in order to obtain stable soliton solutions.