Bonn 2025 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 23: Ultra-cold Atoms, Ions and BEC II (joint session A/Q)
Q 23.3: Talk
Tuesday, March 11, 2025, 11:45–12:00, KlHS Mathe
Josephson dynamics of a finite temperature BEC in a double well potential — •Kateryna Korshynska1,2 and Sebastian Ulbricht1,2 — 1TU Braunschweig, Institut für Mathematische Physik Mendelssohnstr. 3 38106 Braunschweig — 2Physikalisch-Technische Bundesanstalt Bundesallee 100 38116 Braunschweig
A many-particle bosonic system placed in a double-well potential is known to exhibit oscillatory dynamics of the particle populations between the wells. Such collective oscillations are well-known as the Josephson effect and have been intensively investigated both theoretically and experimentally. A well-established approach to describe this dynamics at low temperatures is to assume a two-state model, in which the Josephson equations govern population imbalance and phase difference between the wells. This model is formulated under the assumption that the Bose gas forms a fully coherent system, which holds at zero temperature. However, in typical experiment the finite-temperature BEC is not fully coherent, for instance when the thermal equilibrium is established. To describe this we use the density matrix approach and analyze the influence of higher energy levels on the double-well dynamics. We find that this effect is two-fold: while the higher energy levels below the barrier height contribute to the double-well dynamics, the even more excited particles may lead to thermalization and decoherence.
Keywords: Bose-Einstein condensate; Josephson effect; interference; double-well