%0 Journal Article
%T Condensation of quasiparticles and density modulation beyond the superfluid critical velocity
%A Andras Suto
%A Peter Szepfalusy
%J Physics
%D 2013
%I arXiv
%R 10.1103/PhysRevA.88.043640
%X We investigate the effect of a constant external velocity field on the ground state of a bosonic quasiparticle Hamiltonian. Below a critical velocity the ground state is a quasiparticle vacuum, corresponding to a pure superfluid phase at zero temperature. Beyond the critical velocity energy minimization leads to a macroscopic condensation of quasiparticles at a nonzero wave vector k_v parallel to the velocity v. Simultaneously, physical particles also undergo a condensation at k_v and, to a smaller extent, at -k_v. Together with the BEC at k=0, the three entangled condensates give rise to density modulations of wave vectors k_v and 2k_v. For larger |v| our model predicts a bifurcation of k_v with corresponding two pure condensates and no density modulation.
%U http://arxiv.org/abs/1305.5097v2