2021/01/27 by Ofir E. Alon, Alon, Ofir E., Raphael Beinke +3
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Quantum, superfluid, helium dynamics #Optical properties and cooling technologies in crystalline materials
paper · pdf · doi:10.48550/arxiv.2101.11615
This review explores the dynamics and the low-energy excitation spectra of\nBose-Einstein condensates (BECs) of interacting bosons in external potential\ntraps putting particular emphasis on the emerging many-body effects beyond\nmean-field descriptions. To do so, methods have to be used that, in principle,\ncan provide numerically exact results for both the dynamics and the excitation\nspectra in a systematic manner. Numerically exact results for the dynamics are\npresented employing the well-established multicongurational time-dependent\nHartree for bosons (MCTDHB) method. The respective excitation spectra are\ncalculated utilizing the more recently introduced linear-response theory atop\nit (LR-MCTDHB). The latter theory gives rise to an, in general, non-hermitian\neigenvalue problem. The theory and its newly developed implementation are\ndescribed in detail and benchmarked towards the exactly-solvable\nharmonic-interaction model. Several applications to BECs in one- and\ntwo-dimensional potential traps are discussed. With respect to dynamics, it is\nshown that both the out-of-equilibrium tunneling dynamics and the dynamics of\ntrapped vortices are of many-body nature. Furthermore, many-body effects in the\nexcitation spectra are presented for BECs in different trap geometries. It is\ndemonstrated that even for essentially-condensed systems, the spectrum of the\nlowest-in-energy excitations computed at the many-body level can differ\nsubstantially from the standard mean-field description. In general, it is shown\nthat bosons carrying angular momentum are more sensitive to many-body effects\nthan bosons without. These effects are present in both the dynamics and the\nexcitation spectrum.\n