Quantum phase transitions of atom-molecule Bose mixtures in a double-well potential

TL;DR

This paper investigates quantum phase transitions in atom-molecule Bose mixtures within a double-well potential, revealing second-order and excited state quantum phase transitions with distinct spectral and ground state properties.

Contribution

It introduces the analysis of quantum phase transitions in atom-molecule Bose mixtures, highlighting the occurrence of second-order and excited state transitions in this context.

Findings

Second-order quantum phase transition observed in both atomic and atom-molecule systems.

Degenerate ground state for large attractive interactions.

Discontinuity in the density of states at the ESQPT critical point.

Abstract

The ground state and spectral properties of Bose gases in double-well potentials are studied in two different scenarios: i) an interacting atomic Bose gas, and ii) a mixture of an atomic gas interacting with diatomic molecules. A ground state second-order quantum phase transition (QPT) is observed in both scenarios. For large attractive values of the atom-atom interaction, the ground-state is degenerate. For repulsive and small attractive interaction, the ground-state is not degenerate and is well approximated by a boson coherent state. Both systems depict an excited state quantum phase transition (ESQPT). For the mixed atom-molecule system the critical point of the ESQPT displays a discontinuity in the first derivative of the density of states.