Hannover 2020 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 15: Quantum gases (Bosons) II

Q 15.1: Group Report

Tuesday, March 10, 2020, 11:00–11:30, e214

Bose-Einstein condensates in weak and strong disorder potentials — •Milan Radonjić and Axel Pelster — Physics Department and Research Center OPTIMAS, Technische Universität Kaiserslautern, Germany

Here we consider different generalizations of a perturbative approach to the dirty boson problem, worked out by Huang and Meng within a Bogoliubov theory [1]. At first, we consider a time-dependent extension by considering how switching on and off a weak disorder potential affects the equilibration of an initially homogeneous BEC and the emergence of a disorder-induced condensate deformation. Afterwards, we work out an approach based on the cumulant expansion method [2] up to second order, that is non-perturbative with respect to disorder and also includes quantum fluctuations. We employ it to study static geometric properties of a harmonically trapped molecular BEC in laser speckle potential [3]. For weak disorder we find quantitative agreement with the Huang and Meng theory, while for strong disorder our theory perfectly reproduces the geometric mean of the experimentally measured transverse widths of the column density profiles. Finally, we compare the non-perturbative results of the second and the third order cumulant expansion approach for a homogeneous Bose gas in impurity disorder.

[1] K. Huang and H. F. Meng, Phys. Rev. Lett. 69, 644 (1992)

[2] M. Radonjic et al., New J. Phys. 20, 055014 (2018)

[3] B. Nagler, M. Radonjić, et al., arXiv:1911.02626