Equilibrium phases of dipolar lattice bosons in the presence of random diagonal disorder

Abstract

Ultracold gases offer an unprecedented opportunity to engineer disorder and interactions in a controlled manner. In an effort to understand the interplay between disorder, dipolar interaction and quantum degeneracy, we study two-dimensional hard-core dipolar lattice bosons in the presence of on-site bound disorder. Our results are based on large-scale path-integral quantum Monte Carlo simulations by the Worm algorithm. We study the ground state phase diagram at fixed half-integer filling factor for which the clean system is either a superfluid at lower dipolar interaction strength or a checkerboard solid at larger dipolar interaction strength. We find that, even for weak dipolar interaction, superfluidity is destroyed in favor of a Bose glass at relatively low disorder strength. Interestingly, in the presence of disorder, superfluidity persists for values of dipolar interaction strength for which the clean system is a checkerboard solid. At fixed disorder strength, as the dipolar interaction is increased, superfluidity is destroyed in favor of a Bose glass. As the interaction is further increased, the system eventually develops extended checkerboard patterns in the density distribution. Due to the presence of disorder, though, grain boundaries and defects, responsible for a finite residual compressibility, are present in the density distribution. Finally, we study the robustness of the superfluid phase against thermal fluctuations.

Characterizing the phase diagram of finite-size dipolar Bose-Hubbard systems

“…We observe that all three order parameters point to a first-order transition from a DW to a SF at a critical (V /J) c that only depends on the system size. For the largest system we have simulated, 16 × 8, this is (V /J) c ≈ 3.9, which should be compared with the value (V /J) c ≈ 3.5 obtained for the thermodynamic limit by quantum Monte Carlo methods [8].…”

“…More generally, the entanglement entropy appears as the most flexible tool to detect phase transitions [31][32][33][34]. This set of observables allows us to identify a supersolid phase in the system [7][8][9], which we find to be very sensitive to finite-size effects.…”

“…However, interactions between neutral alkali atoms are usually of very short range. This precludes their use in studying systems with long-range interactions, for which theoretical calculations point to the existence of exotic phases including supersolid order [7][8][9], and spin-glass [10] and spin-ice [11] phases. A number of experimental platforms are being developed to study long-range strongly-correlated phases, from atomic ions in Penning traps [12,13], to systems with dipole-dipole interactions (DDI) such as Rydberg atoms [14][15][16], highly-magnetic atoms [17][18][19][20][21], or ultracold molecules [22][23][24].…”

The Effect of Disorder on the Phase Diagrams of Hard-Core Lattice Bosons With Cavity-Mediated Long-Range and Nearest-Neighbor Interactions

“…The study of adding disorder to the interacting manybody bosonic systems attracts enormous attention both experimentally and theoretically [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Experimentally, ultracold atoms in optical lattices are a promising tool to study quantum phases and quantum phase transitions in strongly correlated quantum many-body systems.…”

Phase diagrams of the disordered Bose-Hubbard model with cavity-mediated long-range and nearest-neighbor interactions

“…A certain degree of disorder is ubiquitous in all condensed matter, but a thorough understanding of these systems is impeded by a poor control over the disorder and competing interactions. On the other hand, ultracold atoms, especially bosons in an optical lattice become an important way to simulate condensed matter systems [1][2][3][4][5][6][7][8][9][10][11][12][13]. In these experiments, interactions and disorder can be tuned independently.…”