Date: Oct 20, Wednesday 3: 00 p.m.

Venue:Conference Hall 322, Science Building,Tsinghua/清华大学高等研究院 科学馆322报告厅

Title: Fragmented Many-Body Ground States for Scalar Bosons in a Single Trap

Speaker: Uwe Fischer (Associate Professor) Seoul National University

Abstract: We investigate whether the many-body states of bosons in a generalized two-mode model with arbitrary long-range interactions and single-

particle orbitals are coherent or fragmented. It is demonstrated that fragmentation can take place in a single trap for positive values of

the interaction couplings, implying that the system is potentially stable. Fragmentation in terms of the single-particle density matrix

is owed to a positive coupling constant in front of the boson pair exchange term in the Hamiltonian. As an application, we have derived

fragmentation of the condensate in the weakly confining directions of quasi-1D respectively quasi-2D gases into mutually incoherent

macroscopic pieces, upon increasing a dimensionless interaction measure beyond a critical value. Fragmented condensate many-body

states in low-dimensional systems therefore occur well before the thermodynamic limit of infinite extension is reached, in which phase

fluctuations of the matter wave field create an infinite number of non-macroscopic fragments.