Bogoliubov depletion of the fragmented condensate in the bosonic flux ladder

Abstract

We theoretically analyze the ground state of weakly interacting bosons in the flux ladder—the system that has been recently realized by means of ultracold atoms in the specially designed optical lattice [M. Atala, M. Aidelsburger, M. Lohse, J. T. Barreiro, B. Paredes, and I. Bloch, Nat. Phys. 10, 588 (2014)]. It is argued that, for the system parameters corresponding to two degenerate minima in the Bloch dispersion relation, the ground state is a fragmented condensate. We study the Bogoliubov depletion of this condensate and discuss the role of boundary conditions.