-orbital Bands

We study a model of interacting two-species bosons that occupy the first excited p-band states of a
two-dimensional square lattice. By exactly solving a single-site problem, we first identify that when
the interaction acquires a SU(2) invariance between two-species, bosons favor minimal total spin
and orbital angular momentum. This is against the well-known Hund's first and second rules for
electrons filling in atomic shells, in which total spin of electrons is maximized and then, compatible
with the first rule, orbital angular momentum is maximized. Such anti-Hund's rule forbids the
Mott insulting phase for odd number of bosons per site. We then investigate the boundary of
superfluid to even-integer filling Mott-insulator transitions analytically within a variational ansatz
that incorporates singlet-paired condensate. <div id="gtx-trans" style="position: absolute; left: 500px; top: -7px;"> <div class="gtx-trans-icon"> </div> </div>