Phase transitions are ubiquitous in our three-dimensional world. By contrast, most conventional do not occur infinite uniform low-dimensional systems because of the increased role thermal fluctuations. The crossover between these situations constitutes an important issue, dramatically illustrated by Bose-Einstein condensation: a gas strongly confined along one direction space may condense this without exhibiting true long-range order perpendicular plane. Here we explore transverse...

We create supercurrents in annular two-dimensional Bose gases through a temperature quench of the normal-to-superfluid phase transition. detect amplitude and chirality these by measuring spiral patterns resulting from interference cloud with central reference disk. These measurements demonstrate stochastic nature supercurrents. further measure their distribution for different times compare it predictions based on Kibble-Zurek mechanism.

Using in situ measurements on a quasi-two-dimensional, harmonically trapped $^{87}\mathrm{Rb}$ gas, we infer various equations of state for the equivalent homogeneous fluid. From dependence total atom number and central density our clouds with chemical potential temperature, obtain pressure phase-space density. Then, using approximate scale invariance this 2D system, determine entropy per particle find very low values (below $0.1{k}_{B}$) strongly degenerate regime. This shows that gas can...

We demonstrate a versatile method for creating state-dependent optical lattices by applying magnetic field gradient modulated in time. This allows tuning the relative amplitude and sign of tunneling different internal states. observe substantially momentum distributions depending on spin state fermionic ^{40}K atoms. Using dipole oscillations, we probe spin-dependent band structure find good agreement with theory. In situ expansion dynamics that one can be completely localized while others...

Absorption imaging with quasi-resonant laser light is a commonly used technique for probing ultra-cold atomic gases in various geometries. In this paper, we investigate some non-trivial aspects of method when applying the to situ diagnosis quasi-two-dimensional (2D) gas. Using Monte Carlo simulations study modification absorption cross-section photon it undergoes multiple scattering We determine variations optical density parameters, such as detuning from resonance and thickness compare our...

We study the dynamics and timescales of a periodically driven Fermi-Hubbard model in three-dimensional hexagonal lattice. The evolution Floquet many-body state is analyzed by comparing it to an equivalent implementation undriven systems. double occupancies for near- off-resonant driving regime indicate that effective Hamiltonian picture valid several orders magnitude modulation time. Furthermore, we show lattice compared simple cubic allows us modulate system up 1 s, corresponding hundreds...

We report on the observation of anti-ferromagnetic correlations ultracold fermions in a variety optical lattice geometries that are well described by Hubbard model, including dimers, 1D chains, ladders, isolated and coupled honeycomb planes, as square cubic lattices. The dependence strength spin specific geometry is experimentally studied measuring along different tunneling links, where redistribution between links observed. By crossover distinct geometries, we demonstrate an effective...

We realize and study the ionic Hubbard model using an interacting two-component gas of fermionic atoms loaded into optical lattice. The bipartite lattice has a honeycomb geometry with staggered energy offset that explicitly breaks inversion symmetry. Distinct density-ordered phases are identified noise correlation measurements atomic momentum distribution. For weak interactions induces charge density wave. strong repulsive we detect suppression doubly occupied sites, as expected for Mott...

Near-resonant periodic driving of quantum systems promises the implementation a large variety novel states, though their preparation and measurement remains challenging. We address these aspects in model system consisting interacting fermions periodically driven array double wells created by an optical lattice. The singlet triplet fractions occupancy Floquet states are measured behavior as function interaction strength is analyzed high- low-frequency regimes. demonstrate full control state...

We study experimentally and numerically the equilibrium density profiles of a trapped two-dimensional $^{87}$Rb Bose gas, investigate equation state homogeneous system using local approximation. find clear discrepancy between in-situ measurements Quantum Monte Carlo simulations, which we attribute to non-linear variation optical atomic cloud with its spatial density. However, good agreement experiment theory is recovered for measured after time-of-flight, taking advantage their...

We perform an ab initio comparison between nonequilibrium dynamical mean-field theory and optical lattice experiments by studying the time evolution of double occupations in periodically driven Fermi-Hubbard model. For off-resonant driving, range validity a description terms effective static Hamiltonian is determined its breakdown due to energy absorption close resonance demonstrated. near-resonant we investigate response change driving amplitude discover asymmetric excitation spectrum with...

We present a general ``fit-free'' method for measuring the equation of state (EoS) scale-invariant gas. This method, which is inspired from procedure introduced by Ku et al. [Science 335, 563 (2012)] unitary three-dimensional Fermi gas, provides formalism can be readily applied to any quantum gas in known trapping potential, frame local density approximation. implement this on weakly interacting two-dimensional Bose across Berezinskii-Kosterlitz-Thouless transition and determine its EoS with...

We propose and analyze a general scheme to create chiral topological edge modes within the bulk of two-dimensional engineered quantum systems. Our method is based on implementation interfaces, designed system, where topologically-protected localize freely propagate in unidirectional manner. This illustrated through an optical-lattice realization Haldane model for cold atoms, additional spatially-varying lattice potential induces distinct phases separated regions space. present two realistic...

We report the observation of all-optically tunable Raman fluorescence from a single quantum dot. The photons are produced in an optically driven $\ensuremath{\Lambda}$ system defined by subjecting electron charged dot to magnetic field Voigt geometry. Detuning driving laser resonance, we tune frequency about 2.5 GHz. number scattered and linewidth investigated as function detuning. study presented here could form basis new technique for investigating spin-bath interactions solid state.