Symmetry Breaking in Bose-Einstein Condensates Confined by a Funnel Potential

Abstract: In this work, we consider a Bose-Einstein condensate in the self-focusing regime, confined transversely by a funnel-like potential and axially by a double-well potential formed by the combination of two inverted P\"oschl-Teller potentials. The system is well described by a one-dimensional nonpolynomial Schr\"odinger equation, for which we analyze the symmetry break of the wave function that describes the particle distribution of the condensate. The symmetry break was observed for several interaction strength values as a function of the minimum potential well. A quantum phase diagram was obtained, in which it is possible to recognize the three phases of the system, namely, symmetric phase (Josephson), asymmetric phase (spontaneous symmetry breaking - SSB), and collapsed states, i.e., those states for which the solution becomes singular, representing unstable solutions for the system. We analyzed our symmetric and asymmetric solutions using a real-time evolution method, in which it was possible to confirm the stability of the results. Finally, a comparison with the cubic nonlinear Schr\"odinger equation and the full Gross-Pitaevskii equation were performed to check the accuracy of the effective equation used here.