Two-dimensional Bose gas of tilted dipoles: roton instability and   condensate depletion
  We predict the effect of the roton instability for a two-dimensional weakly interacting gas of tilted dipoles in a single homogeneous quantum layer. Being typical for strongly correlated systems, the roton phenomena appear to occur in a weakly interacting gas. It is important that in contrast to a system of normal to wide layer dipoles, breaking of the rotational symmetry for a system of tilted dipoles leads to the convergence of the condensate depletion even up to the threshold of the roton instability, with mean-field approach being valid. Predicted effects can be observed in a wide class of dipolar systems. We suggest observing predicted phenomena for systems of ultracold atoms and polar molecules in optical lattices, and estimate optimal experimental parameters. 
A.K. Fedorov, I.L. Kurbakov, Y.E. Shchadilova, Yu.E. Lozovik
cond-mat.quant-gas cond-mat.mes-hall