Alladi Ramakrishnan Hall

Superfluid-insulator transition of two-species bosons with spin-orbit coupling

Saptarshi Mandal

IACS, Kolkata

We study Mott phases and superfluid-insulator (SI) transitions of two-species
ultracold bosonic atoms in a two-dimensional square optical lattice with
nearest-neighbor hopping amplitude t and a spin-orbit coupling γ. Using both
strong-coupling expansion and Gutzwiller mean-field theory, we chart out the
phase diagrams for this system. We compute the momentum distribution of the
bosons in the Mott phase near the SI transition point which displays
characteristics controllable precursor peaks. We analysis the critical theory
of the transition unravels the presence of unconventional quantum critical
points at t/γ=0, which are accompanied by emergence of an additional gapless
mode in the critical region. We also study the superfluid phases of the bosons
near the SI transition using a Gutzwiller mean-field theory that reveals the
existence of a twisted superfluid phase. Finally, we compute the collective
modes of the bosons and point out the presence of reentrant SI transitions as a
function of γ for nonzero t.