Quantum phases and phase transitions of frustrated hard-core bosons on a triangular ladder

Abstract

Kinetically frustrated bosons at half filling in the presence of a competing nearest-neighbor repulsion support a wide supersolid regime on the two-dimensional triangular lattice. We study this model on a two-leg ladder using the finite-size density-matrix renormalization-group method, obtaining a phase diagram which contains three phases: a uniform superfluid (SF), an insulating charge density wave (CDW) crystal, and a bond ordered insulator (BO). We show that the transitions from SF to CDW and SF to BO are continuous in nature, with critical exponents varying continuously along the phase boundaries, while the transition from CDW to BO is found to be first order. The phase diagram is also found to contain an exactly solvable Majumdar Ghosh point, and reentrant SF to CDW phase transitions.

Supersolid in a one-dimensional model of hard-core bosons

“…The SF phase might be stabilized over a larger part of the phase diagram and be easier to detect if we choose a different set of parameters, say |t ′ | < t. As we have seen in our previous work, for such a choice of parameters, it is possible to obtain a regular superfluid phase even exactly at half-filling [25] and it is quite likely that this phase will remain over a fairly large part of the phase diagram even when we move away from half-filling. However, for these parameters, it is likely that the SS phase will occupy a smaller region of the phase diagram.…”

“…We compute various physical quantities to characterize the different phases. Some of these quantities have been calculated by us using the DMRG method to study related models [25,28]. We describe below the quantities which are most important for the characterization of the different phases.…”

“…[25], this model does not have a simple representation in terms of spinless fermions due to the presence of the next-nearest-neighbour hopping term. At half filling and for V = 0, apart from the trivial point t ′ = 0, there exists one more point corresponding to t ′ = −t/2, where the exact ground state can be obtained [25].…”

“…1 has been studied recently by us at half filling [25]. The ground state phase diagram has three different phases, a uniform superfluid (SF), an insulating charge density wave (CDW) crystal and a bond ordered insulator (BO).…”

Hard-core bosons in a zig-zag optical superlattice

“…Later studies of softcore bosons in optical superlattices [18,19] termed these phases as superlattice induced Mott insulator(SLMI) phases. Recent studies on models dealing with the interplay between frustration imposed by geometry and inter- actions have revealed rich physics with a variety of novel phases being exhibited [20][21][22][23].…”