499 research outputs found
Interacting bosons in generalized zig-zag and railroad-trestle models
We theoretically study the ground-state phase diagram of strongly interacting
bosons on a generalized zig-zag ladder model, the rail-road trestle (RRT)
model. By means of analytical arguments in the limits of decoupled chains and
the case of vanishing fillings as well as extensive DMRG calculations we
examine the rich interplay between frustration and interaction for various
parameter regimes. We distinguish three different cases, the fully frustrated
RRT model where the dispersion relation becomes doubly degenerate and an
extensive chiral superfluid regime is found, the anti-symmetric RRT with
alternating and fluxes through the ladder plaquettes and the sawtooth
limit, which is closely related to the latter case. We study detailed phase
diagrams which include besides different single component superfluids, the
chiral superfluid phases, the two component superfluids and different gaped
phases, with dimer and a charge-density wave order.Comment: 10 pages, 16 figure
Three-body constrained bosons in double-well optical lattice
We analyse the ground-state properties of three-body constrained bosons in a
one dimensional optical lattice with staggered hoppings analogous to the double
well optical lattice. By considering attractive and repulsive on-site
interactions between the bosons, we obtain the phase diagram which exhibits
various quantum phases. Due to the double-well geometry and three-body
constraint several gapped phases such as the Mott insulators and
dimer/bond-order phases emerge at commensurate densities in the repulsive
interaction regime. Attractive interaction leads to the pair formation which
leads to the pair bond order phase at unit filling which resembles the
valence-bond solid phase of composite bosonic pairs. At incommensurate
densities we see the signatures of the gapless pair superfluid phase.Comment: 10 pages, 19 figure
Polar molecules in frustrated triangular ladders
Polar molecules in geometrically frustrated lattices may result in a very
rich landscape of quantum phases, due to the non-trivial interplay between
frustration, and two- and possibly three-body inter-site interactions. In this
paper, we illustrate this intriguing physics for the case of hard-core polar
molecules in frustrated triangular ladders. Whereas commensurate lattice
fillings result in gapped phases with bond-order and/or density-wave order, at
incommensurate fillings we find chiral-, two-component-, and pair-superfluids.
We show as well that, remarkably, polar molecules in frustrated lattices allow,
for the first time to our knowledge, for the observation of bond-ordered
supersolids
Anomalous pairing of bosons: Effect of multi body interactions in optical lattice
An interesting first order type phase transition between Mott lobes has been
reported in Phys. Rev. Lett. 109, 135302 (2012) for a two-dimensional
Bose-Hubbard model in the presence of attractive three-body interaction. We
re-visit the scenario in a system of ultracold bosons in a one-dimensional
optical lattice using the density matrix renormalization group method and show
that an unconventional pairing of particles occurs due to the competing
two-body repulsive and three-body attractive interactions. This leads to a pair
superfluid phase sandwiched between the Mott insulator lobes corresponding to
densities and in the strongly interacting regime. We further
extend our analysis to a two dimensional Bose-Hubbard model using the self
consistent cluster-mean-field theory approach and confirm that the
unconventional pair superfluid phase stabilizes in the region between the Mott
lobes in contrast to the direct first order jump as predicted before. In the
end we establish connection to the most general Bose-Hubbard model and analyse
the fate of the pair superfluid phase in presence of an external trapping
potential.Comment: 5 pages, 6 figure
Supersolid in a one-dimensional model of hard-core bosons
We study a system of hardcore boson on a one-dimensional lattice with
frustrated next-nearest neighbor hopping and nearest neighbor interaction. At
half filling, for equal magnitude of nearest and next-nearest neighbor hopping,
the ground state of this system exhibits a first order phase transition from a
Bond-Ordered (BO) solid to a Charge-Density-Wave(CDW) solid as a function of
the nearest neighbor interaction. Moving away from half filling we investigate
the system at incommensurate densities, where we find a SuperSolid (SS) phase
which has concurrent off-diagonal long range order and density wave order which
is unusual in a system of hardcore bosons in one dimension. Using the
finite-size Density-Matrix Renormalization Group (DMRG) method, we obtain the
complete phase diagram for this model
Phases and phase transitions of frustrated hard-core bosons on a triangular ladder
We study hardcore bosons on a triangular ladder at half filling in the
presence of a frustrating hopping term and a competing nearest neighbor
repulsion which promotes crystallization. Using the finite-size
density-matrix renormalization group method, we obtain the phase diagram which
contains three phases: a uniform superfluid (SF), an insulating charge density
wave (CDW) crystal and a bond ordered insulator (BO). We find that the
transitions from SF to CDW and SF to BO are continuous in nature, with critical
exponents varying continously along the phase boundaries, while the transition
from CDW to BO is found to be first order. The phase diagram is also shown to
contain an exactly solvable Majumdar Ghosh point, and re-entrant SF to CDW
phase transitions.Comment: 10 pages, 16 figure
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