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Register a new userPhase Structure of Repulsive Hard-Core Bosons in a Stacked Triangular Lattice
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In this paper, we study phase structure of a system of hard-core bosons with a nearest-neighbor (NN) repulsive interaction in a stacked triangular lattice. Hamiltonian of the system contains two parameters one of which is the hopping amplitude $t$ between NN sites and the other is the NN repulsion $V$. We investigate the system by means of the Monte-Carlo simulations and clarify the low and high-temperature phase diagrams. There exist solid states with density of boson $rho={1 over 3}$ and ${2over 3}$, superfluid, supersolid and phase-separated state. The result is compared with the phase diagram of the two-dimensional system in a triangular lattice at vanishing temperature.
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We numerically demonstrate that a supersolid phase exists in a frustrated hard-core boson system on a triangular lattice over a wide range of interaction strength. In the infinite repulsion (Ising) limit, we establish a mapping to the same problem with unfrustrated hopping, which connects the supersolid to the known results in that case. The weak superfluidity can be destroyed or strongly enhanced by a next nearest neighbor hopping term, which provides valuable information for experimental realization of a supersolid phase on optical lattice.
Spin liquids occuring in 2D frustrated spin systems were initially assumed to appear at strongest frustration, but evidence grows that they more likely intervene at transitions between two different types of order. To identify if this is more general, we here analyze a generalization of the spatially anisotropic triangular lattice (SATL) with antiferromagnetic XY interactions, the spatially emph{completely} anisotropic triangular lattice (SCATL). This model can be implemented in experiments with trapped ions, ultra-small Josephson junctions, or ultracold atoms in optical lattices. Using Takahashis modified spin-wave theory, we find indications that indeed two different kinds of order are always separated by phases without magnetic long-range order. Our results further suggest that two gapped, magnetically-disordered phases, identified as distinct in the SATL, are actually continuously connected via the additional anisotropy of the SCATL. As these results indicate, this additional anisotropy -- allowing to approach quantum-disordered phases from different angles -- can give fundamental insight into the nature of quantum disordered phases. We complement our results by exact diagonalizations, which also indicate that in part of the gapped non-magnetic phase, chiral long-range correlations could survive.
In this paper, we study phase diagrams of dipolar hard-core boson gases on the honeycomb lattice. The system is described by the Haldane-Bose-Hubbard model with complex hopping amplitudes and the nearest neighbor repulsion. By using the slave-particle representation of the hard-core bosons and also the path-integral quantum Monte-Carlo simulations, we investigate the system and to show that the systems have a rich phase diagram. There are Mott, superfluid, chiral superfluid, and sublattice chiral superfluid phases as well as the density-wave phase. We also found that there exists a coexisting phase of superfluid and chiral superfluid. Critical behaviors of the phase transitions are also clarified.
Using large-scale quantum Monte Carlo simulations we study bosons hopping on a triangular lattice with nearest (V) and next-nearest (V) neighbor repulsive interactions. In the limit where V=0 but V is large, we find an example of an unusual period-three striped supersolid state that is stable at 1/2-filling. We discuss the relationship of this state to others on the rich ground-state phase diagram, which include a previously-discovered nearest-neighbor supersolid, a uniform superfluid, as well as several Mott insulating phases. We study several superfluid- and supersolid-to-Mott phase transitions, including one proposed by a recent phenomenological dual vortex field theory as a candidate for an exotic deconfined quantum critical point. We find no examples of unconventional quantum criticality among any of the interesting phase transitions in the model.
In this paper, we consider the bosonic t-J model, which describes two-component hard-core bosons with a nearest-neighbor (NN) pseudo-spin interaction and a NN hopping. To study phase diagram of this model, we derive effective field theories for low-energy excitations. In order to represent the hard-core nature of bosons, we employ a slave-particle representation. In the path-integral quantization, we first integrate our the radial degrees of freedom of each boson field and obtain the low-energy effective field theory of phase degrees of freedom of each boson field and an easy-plane pseudo-spin. Coherent condensates of the phases describe, e.g., a magnetic order of the pseudo-spin, superfluidity of hard-core bosons, etc. This effective field theory is a kind of extended quantum XY model, and its phase diagram can be investigated precisely by means of the Monte-Carlo simulations. We then apply a kind of Hubbard-Stratonovich transformation to the quantum XY model and obtain the second-version of the effective field theory, which is composed of fields describing the pseudo-spin degrees of freedom and boson fields of the original two-component hard-core bosons. As application of the effective-field theory approach, we consider the bosonic t-J model on the square lattice and also on the triangular lattice, and compare the obtained phase diagrams with the results of the numerical studies. We also study low-energy excitations rather in detail in the effective field theory. Finally we consider the bosonic t-J model on a stacked triangular lattice and obtain its phase diagram. We compare the obtained phase diagram with that of the effective field theory to find close resemblance.
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