Supersolids versus Phase Separation in Two-Dimensional Lattice Bosons

We studied all possible ground states, including supersolid (SS) phases and phase separations of hard-core-and soft-core-extended Bose-Hubbard models with fixed boson densities by using the Gutzwiller variational wave function and the linear programming method. We found that the phase diagram of the soft-core model depends strongly on its transfer integral. Furthermore, for a large transfer integral, we showed that an SS phase can be the ground state even below or at half filling against the phase separation. We also found that the density difference between nearest-neighbor sites, which indicates the density order of the SS phase, depends strongly on the boson density and transfer integral.

Section: A Half Fillingsupporting

confidence: 78%

Section: A Half Fillingmentioning

confidence: 95%

Gutzwiller study of extended Hubbard models with fixed boson densities

Kimura

2011

“…Thus, experiments with polar molecules go beyond quantum simulation of effective theories motivated by electronic systems and aim at exploring a genuinely new domain of many-body quantum behavior, unique to dipolar interactions. Dipolar interactions can be utilized to generate long-range interactions of arbitrary shape using microwave fields [11], simulate exotic spin Hamiltonians [12,13] and are theoretically predicted to give rise to numerous interesting collective phenomena such as roton softening [14][15][16], supersolidity [17][18][19][20][21], p-wave superfluidity [22], emergence of artificial photons [23], bilayer quantum phase transitions [24], multi-layer self-assembled chains [25] for bosonic molecules, dimerization and inter-layer pairing [26,27], spontaneous inter-layer coherence [28], itinerant ferroelectricity [29], anisotropic Fermi liquid theory and anisotropic sound modes [30][31][32][33], fractional quantum Hall effect [34], Wigner crystallization [35], density-wave and striped order [36,37], biaxial nematic phase [38], topological superfluidity [39] and Z 2 topological phase [40], just to mention a few.…”

Section: Introductionmentioning

confidence: 99%

Collective phenomena in a quasi-two-dimensional system of fermionic polar molecules: Band renormalization and excitons

Babadi

Demler

2011

We theoretically analyze a quasi-two-dimensional system of fermionic polar molecules in a harmonic transverse confining potential. The renormalized energy bands are calculated by solving the Hartree-Fock equation numerically for various trap and dipolar interaction strengths. The inter-subband excitations of the system are studied in the conserving time-dependent Hartree-Fock (TDHF) approximation from the perspective of lattice modulation spectroscopy experiments. We find that the excitation spectrum consists of both intersubband particle-hole excitation continuums and anti-bound excitons, arising from the anisotropic nature of dipolar interactions. The excitonic modes capture the majority of the spectral weight. We also evaluate the inter-subband transition rates in order to investigate the nature of the excitonic modes and find that they are antibound states formed from particle-hole excitations arising from several subbands. Our results indicate that the excitonic effects are present for interaction strengths and temperatures accessible in current experiments with polar molecules. I. INTRODUCTIONIn the past decade, much of the experimental and theoretical progress in the field of ultracold atoms [1][2][3] are motivated by the prospect of realizing novel strongly correlated many-body states of matter. In particular, experimental realization of quantum degenerate gases of fermionic polar molecules has witnessed a very rapid progress. By association of atoms via a Feshbach resonance to form deeply bound ultracold molecules [4,5], a nearly degenerate gas of KRb polar molecules in their rotational and vibrational ground state has been recently realized [6][7][8][9][10]. The molecules can be polarized by applying a d.c. electric field, resulting in strong dipole-dipole inter-molecular interactions.A strikingly new feature of systems of fermionic polar molecules is the anisotropy of dipolar interactions, making them unparalleled among the traditional condensed matter systems. Thus, experiments with polar molecules go beyond quantum simulation of effective theories motivated by electronic systems and aim at exploring a genuinely new domain of many-body quantum behavior, unique to dipolar interactions. Dipolar interactions can be utilized to generate long-range interactions of arbitrary shape using microwave fields [11], simulate exotic spin Hamiltonians [12,13] and are theoretically predicted to give rise to numerous interesting collective phenomena such as roton softening [14][15][16] Despite the theoretical prediction of numerous exotic quantum many-body phenomena in polar molecules, realization and observation of many of these novel predictions are still an experimental challenge. At the time this paper was written, the coldest gas of fermionic polar molecules has been realized with KRb molecules at a temperature of 1.4 T F [6-10], where T F is the Fermi temperature. The majority of the mentioned quantum phenomena require strong suppression of thermal fluctuations, i.e. strong degeneracy condition (T T F ).A major...

“…Using the operator-loop cluster update, the autocorrelation time for the system sizes we consider here is at most a few Monte Carlo sweeps for the entire range of parameter space explored. The simulations are carried out on finite lattices with L 2 sites for L up to 32 at temperatures sufficiently low in order to resolve ground-state properties of this finite system [43]. Estimates of physical observables in the thermodynamic limit are obtained from simultaneous finite-size and finite-temperature extrapolation to the L → ∞, β → ∞ limit.…”

Section: Quantum Monte-carlomentioning

confidence: 99%

“…In section II, we introduce the model, summarize the basic properties of the energy imbalanced honeycomb lattice, in particular the Berry curvature and we present the two approaches used in the paper: the quantum Monte-Carlo method (QMC) [40][41][42][43] and the Gutzwiller ansatz (GA) [44][45][46]. In section III, we present our numerical results: the ground state phase diagram and the excitations, emphasizing that they depict non-vanishing Berry curvature.…”

Section: Introductionmentioning

confidence: 99%

Berry curvature of interacting bosons in a honeycomb lattice

Sengupta

Batrouni

et al. 2015

Self Cite

We consider soft-core bosons with onsite interaction loaded in the honeycomb lattice with different site energies for the two sublattices. Using both a mean-field approach and quantum Monte-Carlo simulations, we show that the topology of the honeycomb lattice results in a non-vanishing Berry curvature for the band structure of the single-particle excitations of the system. This Berry curvature induces an anomalous Hall effect. It is seen by studying the time evolution of a wavepacket, namely a superfluid ground state in a harmonic trap, subjected either to a constant force (Bloch oscillations) or to a sudden shift of the trap center.