Super-Tonks-Girardeau quench of dipolar bosons in a one-dimensional optical lattice

A super-Tonks-Giradeau gas is a highly excited yet stable quantum state of strongly attractive bosons confined to one dimension. This state can be obtained by quenching the interparticle interactions from the ground state of a strongly repulsive Tonks-Girardeau gas to the strongly attractive regime. While the super-Tonks-Girardeau quench with contact interactions has been thoroughly studied, less is known about the stability of such a procedure when long-range interactions come into play. This is a particularly important question in light of recent advances in controlling ultracold atoms with dipole-dipole interactions. In this study, we thus simulate a super-Tonks-Girardeau quench on dipolar bosons in a one-dimensional optical lattice and investigate their dynamics for many different initial states and fillings. By calculating particle density, correlations, entropy measures, and natural occupations, we establish the regimes of stability as a function of dipolar interaction strength. For an initial unit-filled Mott state, stability is retained at weak dipolar interactions. For cluster states and doubly-filled Mott states, instead, dipolar interactions eventually lead to complete evaporation of the initial state and thermalization consistent with predictions from random matrix theory. Remarkably, though, dipolar interactions can be tuned to achieve longer-lived prethermal states before the eventual thermalization. Our study highlights the potential of long-range interactions to explore new mechanisms to steer and stabilize excited quantum states of matter.Comment: 16 pages, 17 figures, 4 appendice

Exploring limits of dipolar quantum simulators with ultracold molecules

We provide a quantitative blueprint for realizing two-dimensional quantum simulators employing ultracold dipolar molecules or magnetic atoms by studying their accuracy in predicting ground state properties of lattice models with long-range interactions. For experimentally relevant ranges of potential depths, interaction strengths, particle fillings, and geometric configurations, we map out the agreement between the state prepared in the quantum simulator and the target lattice state. We do so by separately calculating numerically exact many-body wave functions in the continuum and single- or multi-band lattice representations, and building their many-body state overlaps. While the agreement between quantum simulator and single-band models is good for deep optical lattices with weaker interactions and low particle densities, the higher band population rapidly increases for shallow lattices, stronger interactions, and in particular above half filling. This induces drastic changes to the properties of the simulated ground state, potentially leading to false predictions. Furthermore, we show that the interplay between commensurability and interactions can lead to quasidegeneracies, rendering a faithful ground state preparation even more challenging.Comment: 8 pages, 4 figures; supplementary material available with 8 pages, 4 figure

Superlattice switching from parametric instabilities in a driven-dissipative BEC in a cavity

We numerically obtain the full time-evolution of a parametrically-driven dissipative Bose-Einstein condensate in an optical cavity and investigate the implications of driving for the phase diagram. Beyond the normal and superradiant phases, a third nonequilibrium phase emerges as a manybody parametric resonance. This dynamical normal phase switches between two symmetry-broken superradiant configurations. The switching implies a breakdown of the system's mapping to the Dicke model. Unlike the other phases, the dynamical normal phase shows features of nonintegrability and thermalization.Comment: 5 pages, 3 figure

Sensing Floquet-Majorana fermions via heat transfer

Time periodic modulations of the transverse field in the closed XY spin-1/2 chain generate a very rich dynamical phase diagram, with a hierarchy of Z_n topological phases characterized by differing numbers of Floquet-Majorana modes. This rich phase diagram survives when the system is coupled to dissipative end reservoirs. Circumventing the obstacle of preparing and measuring quasienergy configurations endemic to Floquet-Majorana detection schemes, we show that stroboscopic heat transport and spin density are robust observables to detect both the dynamical phase transitions and Majorana modes in dissipative settings. We find that the heat current provides very clear signatures of these Floquet topological phase transitions. In particular, we observe that the derivative of the heat current, with respect to a control parameter, changes sign at the boundaries separating topological phases with differing nonzero numbers of Floquet-Majorana modes. We present a simple scheme to directly count the number of Floquet-Majorana modes in a phase from the Fourier transform of the local spin density profile. Our results are valid provided the anisotropies are not strong and can be easily implemented in quantum engineered systems

Quench dynamics and scaling laws in topological nodal loop semimetals

We employ quench dynamics as an effective tool to probe different universality classes of topological phase transitions. Specifically, we study a model encompassing both Dirac-like and nodal loop criticalities. Examining the Kibble-Zurek scaling of topological defect density, we discover that the scaling exponent is reduced in the presence of extended nodal loop gap closures. For a quench through a multicritical point, we also unveil a path-dependent crossover between two sets of critical exponents. Bloch state tomography finally reveals additional differences in the defect trajectories for sudden quenches. While the Dirac transition permits a static trajectory under specific initial conditions, we find that the underlying nodal loop leads to complex time-dependent trajectories in general. In the presence of a nodal loop, we find, generically, a mismatch between the momentum modes where topological defects are generated and where dynamical quantum phase transitions occur. We also find notable exceptions where this correspondence breaks down completely.Comment: 8 pages, 7 figures; references adde