Integrability and losses in the dissipative Bose-Hubbard model

by Christopher Gustav Ekman (Stockholm University)

Thursday 20 Nov 2025, 10:00 → 12:00 Europe/Stockholm

A4:3001 (AlbaNova Main Building)

Abstract:
The principal aim of this thesis is to provide an introduction to the topics required for a full
understanding of the attached article [Art. 1], which treats an exactly solvable model that
connects three different areas of quantum many-body physics: open quantum systems with
losses, strongly correlated systems, and disordered systems. It was solved by using the Bethe
ansatz as well as the surrounding machinery of the quantum inverse scattering method. The
exact solution leads to the prediction of several phases of matter which are expected to be
realizable in systems of cold atoms restricted to move in one spatial dimension. At small
interactions, the model describes a set of fragmented condensates, which are reminiscent of a
Bose glass, but with the difference that the condensates are localized to the boundary or
somewhere in the bulk, depending on the strength of the tunnelling amplitude in relation to
the disorder. For strong interactions the model describes a phase similar to a Mott insulator,
with the difference that the particles are localized at the boundary or delocalized, depending
on the strength of the tunnelling amplitude in relation to the interaction strength. In order
build towards this exact solution the thesis also describe open quantum systems and integrable
models in general. In chapter 2, the former is mainly described using the Lindblad and the
Keldysh formalism. This chapter also includes a brief description of the non-hermitian and
Liouvillian skin effects. In chapter 3, integrability is described via the mathematical structure
surrounding the isotropic Heisenberg model. Finally, in chapter 4, the various methods are
applied to the disordered, dissipative Bose-Hubbard model.