Interferometric Order Parameter for Excited-State Quantum Phase Transitions in Bose-Einstein Condensates

Polina Feldmann (1) , Carsten Klempt (1) , Augusto Smerzi (2) , Luis Santos (3) , Manuel Gessner (4)

1 Leibniz Universität Hannover=Leibniz University Hannover
2 INO - Istituto Nazionale di Ottica
3 ITP - Institut für Theoretische Physik [Hannover]
4 LKB [Collège de France] - Laboratoire Kastler Brossel

Excited-state quantum phase transitions extend the notion of quantum phase transitions beyond the ground state. They are characterized by closing energy gaps amid the spectrum. Identifying order parameters for excited-state quantum phase transitions poses, however, a major challenge. We introduce a topological order parameter that distinguishes excited-state phases in a large class of mean-field models and can be accessed by interferometry in current experiments with spinor Bose-Einstein condensates. Our work opens a way for the experimental characterization of excited-state quantum phases in atomic many-body systems.

Mots clés: Quantum phase transitions; Collective dynamics; Spinor Bose-Einstein condensates; Mean field theory; Topology

Domaines: Mécanique statistique [cond-mat.stat-mech]

Polina Feldmann, Carsten Klempt, Augusto Smerzi, Luis Santos, Manuel Gessner. Interferometric Order Parameter for Excited-State Quantum Phase Transitions in Bose-Einstein Condensates. Physical Review Letters, 2021, 126 (23), ⟨10.1103/PhysRevLett.126.230602⟩. ⟨hal-03374664⟩