Abstract
The dipolar quantum gas offers a fascinating platform for understanding the quantum physics of systems equipped with the dipole-dipole interaction. Exotic phases of matter such as the quantum droplets and supersolids have been observed in the dipolar quantum gas, owing to the interplay between s-wave scattering and the dipole-dipole interaction. Nonetheless, the behaviors of dipolar quantum gas in two dimensions and the effect of dipolar interactions in the dynamics of 2D physics remain elusive experimentally. In this thesis, we study the dipolar quantum gas in the quasi-two-dimensional regime which is realized by an optical trapping scheme. We demonstrate the insignificant and significant role of the non-local part of dipolar interactions in a 2D normal gas and a 2D superfluid by observing the crossover of magnetostriction. We further study the influence of dipolar interactions in the Berezinskii-Kosterlitz-Thouless transition which relates to the emergence of 2D superfluid. While the observed shift of critical transition point can be explained by an effective short-range interaction parameter, we find the signature of the anisotropic non-local part of dipolar interactions by measuring the equation-of-state and the number fluctuation in the superfluid regime. The effect of this non-local part of dipolar interactions is further confirmed by observing the break of scale invariance in the dipolar 2D superfluid, which is characterized by the measurement of breathing mode. We also theoretically identify and experimentally observe a supersolid-like stripe arrays in the roton instability regime, opening the pathway to the study of supersolidity in two dimension. Overall, our work illustrate the effect of dipolar interactions in the static and dynamical properties of an ultracold 2D Bose gas, which inspires furture study on the details of the interplay between dipolar interactions and reduced dimensionality.