Density instabilities in multi-layer dipolar Fermi gases

S. G. Bhongale, Ludwig Mathey, Shan-Wen Tsai +2 more

Yi Li, Congjun Wu

Ahmet Keleş, Erhai Zhao

Michele Callegari

Data l'inadeguatezza dell'approssimazione RPA nel descrivere sistemi di ferrioni dipolari. Lo schema STLS viene applicato nello studio di tali sistemi. Si studiano in particolare le instabilita legate alla transizione verso collasso (mono-layer) e stripe phase (multi-layer).

Ahmet Keleş, Erhai Zhao

Experiments on quantum degenerate Fermi gases of magnetic atoms and dipolar molecules begin to probe their broken-symmetry phases dominated by the long-range, anisotropic dipole-dipole interaction. Several candidate phases including the $p$-wave superfluid, the stripe density wave, and a supersolid have been proposed theoretically for two-dimensional spinless dipolar Fermi gases. Yet the phase boundaries predicted by different approximations vary greatly and a definitive phase diagram is still lacking. Here we present a theory that treats all competing many-body instabilities in the particle-particle and particle-hole channel on equal footing. We obtain the low-temperature phase diagram by numerically solving the functional renormalization-group flow equations and find a nontrivial density wave phase at small dipolar tilting angles and strong interactions, but no evidence of the supersolid phase. We also estimate the critical temperatures of the ordered phases.

Meera M. Parish, Francesca Maria Marchetti

We study the density instabilities of a two-dimensional gas of dipolar fermions with aligned dipole moments. The random phase approximation (RPA) for the density-density response function is never accurate for the dipolar gas, and so we incorporate correlations beyond RPA via an improved version of the Singwi-Tosi-Land-Sjölander scheme. In addition to density-wave instabilities, our formalism captures the collapse instability that is expected from Hartree-Fock calculations but is absent from RPA. Crucially, we find that when the dipoles are perpendicular to the layer, the system spontaneously breaks rotational symmetry and forms a stripe phase, in defiance of conventional wisdom.