Description
We investigate the quantum phases of monodispersed
classical and quantum bosonic gases confined to two
dimensions and interacting via a class of soft-shoulder
potentials. The latter correspond to soft-core potentials with
an additional hard-core onsite interaction, and are relevant
both to superconducting materials with multi-scale
intervortex forces and cold atomic gases. Using a
combination of classical molecular dynamics simulations in
free space and exact quantum Monte Carlo simulations on a
lattice, we show that the low temperature phases for weak
and strong interactions following a temperature quench are a
homogeneous (super)fluid and a glass, respectively. The
latter is an insulating phase characterized by inhomogeneity
in the density distribution and structural disorder.
Remarkably, we find that for intermediate interaction
strengths a "superglass" occurs in an extended region of the
quantum phase diagram, where glassy behavior coexists with
a sizable finite superfluid fraction. This glass phase is
obtained in the absence of geometrical frustration or external
disorder and is a result of the competition of quantum
fluctuations and cluster formation in the corresponding
classical ground state. Given the simplicity and generality of
the model, this superglass phases should be directly relevant
for state-of-the-art experiments with Rydberg-dressed atoms
in optical lattices.
