Spontaneous symmetry breaking in coupled Bose-Einstein condensates

Abstract

We study a system of two hardcore bosonic Hubbard models weakly coupled with each other by tunneling. Assuming that the single uncoupled model exhibits off-diagonal long-range order, we prove that the coupled system exhibits spontaneous symmetry breaking (SSB) in the infinite volume limit, in the sense that the two subsystems maintain a definite relative U(1) phase when the tunneling is turned off. Although SSB of the U(1) phase is never observable in a single system, SSB of the relative U(1) phase is physically meaningful and observable by interference experiments. The present theorem is made possible by the rigorous theory of low-lying states and SSB in quantum antiferromagnets developed over the years.

12 pages, no figures

References in corpus (2)

• Many-Body Physics with Ultracold Gases
• Long-range order, "tower" of states, and symmetry breaking in lattice quantum systems

Cited by in corpus (2)

• Exact eigenstates of extended SU($N$) Hubbard models: Generalizations of $\eta$-pairing states with $N$-particle off-diagonal long-range order
• Intercomponent entanglement entropy and spectrum in binary Bose-Einstein condensates