Coherent backscattering in the Fock space of a disordered Bose-Hubbard system
Peter Schlagheck, Université de Liège
Coherent backscattering in disordered or chaotic systems is an ubiquitous wave phenomenon that arises in a number of physical contexts involving classical (e.g. electromagnetic) or quantum (matter) waves. It essentially refers to the coherent enhancement of the backscattering intensity in the direction that is opposite to the propagation of the incident wave. From a semiclassical point of view, this enhancement is caused by the constructive interference of backscattered classical paths with their time-reversed counterparts.
In my talk I shall discuss the generalization of this wave interference phenomenon to the many-body dynamics that takes place within an interacting Bose-Hubbard system. In this particular context, the « classical » paths are given by solutions of a discrete nonlinear Gross-Pitaevskii equation and their « quantum » interference arises within the Fock space of the Bose-Hubbard system. As a consequence, an initially prepared Fock state is, in the course of time evolution (and after averaging over random on-site energies), twice as often encountered as other Fock states of the system with comparable total energy. This semiclassical prediction represents a significant departure from the principle of quantum ergodicity in finite systems and is indeed confirmed by numerical simulations. We argue that an experimental detection of many-body coherent backscattering using ultracold bosonic atoms in optical lattices is within reach.
Ref.: T. Engl, J. Dujardin, A. Argüelles, P. Schlagheck, K. Richter, and J. D. Urbina, Phys. Rev. Lett. 112, 140403 (2014)