Transport of the repulsive Bose-Einstein condensate in a double-well trap: interaction impact and relation to Josephson effect

TL;DR

This paper investigates how interatomic interactions influence the transport of a repulsive Bose-Einstein condensate in a double-well trap, revealing conditions for efficient transfer and its relation to the Josephson effect.

Contribution

It demonstrates that repulsive interactions significantly enhance transport speed and range, and establishes an approximate analogy to the d.c. Josephson effect in this system.

Findings

Interaction supports wider velocity range for transfer

Transport is up to 1000 times faster with interactions

Soft barrier velocity profiles improve robustness

Abstract

Two aspects of the transport of the repulsive Bose-Einstein condensate (BEC) in a double-well trap are inspected: impact of the interatomic interaction and analogy to the Josephson effect. The analysis employs a numerical solution of 3D time-dependent Gross-Pitaevskii equation for a total order parameter covering all the trap. The population transfer is driven by a time-dependent shift of a barrier separating the left and right wells. Sharp and soft profiles of the barrier velocity are tested. Evolution of the relevant characteristics, involving phase differences and currents, is inspected. It is shown that the repulsive interaction substantially supports the transfer making it possible i) in a wide velocity interval and ii) three orders of magnitude faster than in the ideal BEC. The transport can be approximately treated as the d.c. Josephson effect. A dual origin of the critical barrier velocity (break of adiabatic following and d.c.-a.c. transition) is discussed. Following the calculations, robustness of the transport (d.c.) crucially depends on the interaction and barrier velocity profile. Only soft profiles which minimize undesirable dipole oscillations are acceptable.