Particle-Localized Ground State of Atom-Molecule Bose-Einstein Condensates in a Double-Well Potential

TL;DR

This paper investigates how atom-molecule internal tunneling influences the ground state of atom-molecule Bose-Einstein condensates in a double-well potential, revealing a transition from symmetric to particle-localized states driven by effective interactions.

Contribution

It introduces the concept of particle-localized ground states induced by atom-molecule internal tunneling and analyzes the stability and bifurcation behavior of these states.

Findings

Symmetric ground state becomes unstable at a critical tunneling strength.

Ground state bifurcates into particle-localized states beyond the critical point.

Reentrant transition possible at large detuning between atomic and molecular states.

Abstract

We study the effect of atom-molecule internal tunneling on the ground state of atom-molecule Bose-Einstein condensates in a double-well potential. In the absence of internal tunneling between atomic and molecular states, the ground state is symmetric, which has equal-particle populations in two wells. From the linear stability analysis, we show that the symmetric stationary state becomes dynamically unstable at a certain value of the atom-molecule internal tunneling strength. Above the critical value of the internal tunneling strength, the ground state bifurcates to the particle-localized ground states. The origin of this transition can be attributed to the effective attractive inter-atomic interaction induced by the atom-molecule internal tunneling. This effective interaction is similar to that familiar in the context of BCS-BEC crossover in a Fermi gas with Feshbach resonance. Furthermore, we point out the possibility of reentrant transition in the case of the large detuning between the atomic and molecular states.