Interaction Quench Dynamics and Stability of Quantum Vortices in Rotating Bose-Einstein Condensates

We theoretically investigate the non-equilibrium dynamics of quantum vortices in a two-dimensional rotating Bose-Einstein condensate following an interaction quench. Using an ab initio and numerically exact quantum many-body approach, we systematically tune the interplay between interaction strength and angular velocity to prepare quantum vortices in various configurations and examine their post-quench dynamics. Our study reveals distinct dynamical regimes: First, vortex distortion accompanied by density cloud fragmentation, matching the initial vortex number and second, vortex revival, where fragmented densities interact and merge. Notably, we observe complete vortex revival dynamics in the single-vortex case, pseudo-revival in double and triple vortex configurations, and chaotic many-body dynamics in systems with multiple vortices. Our results reveal a universal out-of-equilibrium response of quantum vortices to interaction quenches, highlighting the importance of many-body effects with a possible exploration in quantum simulation with ultracold quantum fluids.

💡 Research Summary

The authors investigate the non‑equilibrium dynamics of quantum vortices in a two‑dimensional rotating Bose‑Einstein condensate (BEC) after an interaction quench, employing the numerically exact Multi‑Configurational Time‑Dependent Hartree for Bosons (MCTDHB) method. The system consists of N = 100 bosons confined in a hard‑wall disk potential, interacting via a short‑range Gaussian‑regularized delta potential. By scanning the rotation frequency Ω (0 → 1) and interaction strength g (0 → 2), they prepare a variety of vortex configurations—single, double, triple, and multi‑vortex states—using four time‑dependent orbitals (M = 4) on a 128 × 128 spatial grid. The degree of fragmentation F = 1 − n₁ (where n₁ is the largest natural orbital occupation) serves as the primary many‑body diagnostic.

Key findings:

1. Fragmentation Landscape – Both Ω and g increase overall fragmentation, but the dependence on Ω is non‑monotonic, displaying peaks and troughs. Stronger interactions populate more orbitals, raising F, while rotation can either enhance or suppress fragmentation depending on the specific Ω value. This reflects a delicate balance between angular momentum imparted by rotation and correlation effects from interactions.

2. Quench‑Induced Vortex Dynamics – After a sudden reduction of g, the initially prepared vortices undergo breathing and distortion, while the overall density splits into a number of fragments equal to the initial vortex count. These fragments rotate opposite to the original sense of rotation and remain dynamically coupled to the fragmented orbitals.

3. Revival Phenomena – For a single vortex, the fragment rotation period matches the revival period of the vortex core, leading to a complete revival of the original vortex profile. In double and triple vortex cases, interference among fragments yields only partial or “pseudo‑revival” where the vortex cores re‑emerge imperfectly. In configurations with many vortices, the nonlinear interaction among fragments generates chaotic dynamics without a clear revival timescale.

4. Mean‑Field Limitations – The Gross‑Pitaevskii (GP) mean‑field equation fails to capture any of the fragmentation, opposite‑sense rotation of density fragments, or the non‑periodic revival behavior. GP reproduces only a coarse vortex shape and underestimates energy transfer to higher orbitals.

5. Temporal Fragmentation Oscillations – The fragmentation measure F itself oscillates in time, synchronizing with the vortex revival cycles for simple configurations, indicating a “dynamical fragmentation” where many‑body correlations are periodically enhanced and suppressed. For stronger interactions (g ≈ 2) F reaches 0.3–0.4, signifying substantial occupation of multiple orbitals even for N = 100.

The study demonstrates that in regimes of strong interactions and rapid rotation, many‑body effects dominate vortex physics, necessitating beyond‑mean‑field approaches such as MCTDHB. The authors propose that experimental verification could be achieved via time‑resolved imaging, phase‑contrast microscopy, or matter‑wave interferometry to observe fragment rotation and revival dynamics. Overall, the work provides a comprehensive map of how interaction quenches reshape vortex structures, highlights the universal out‑of‑equilibrium response of rotating BECs, and establishes a benchmark for future quantum‑simulation experiments with ultracold gases.