"Quantum phases of microwave-dressed molecules"
Recent experimental breakthroughs in preparing and stabilizing ultracold ensembles of heteronuclear molecules have opened new avenues for exploring strongly dipolar quantum matter. In particular, the remarkable degree of control over long-range molecular interactions afforded by precisely tuned microwave fields offers unique opportunities to realize novel phases of dipolar matter and access regimes that challenge conventional descriptions of weakly interacting quantum gases.
Here, we discuss these prospects from different perspectives. First, we employ path-integral quantum Monte Carlo simulations to explore the phase diagram of microwave-dressed molecules across a broad range of interaction strengths and particle numbers. The peculiar form of the microwave-induced interactions is found to stabilize self-bound quantum droplets and drive transitions to two-dimensional superfluids and freely suspended superfluid membranes with a thickness of only a single molecule. At stronger interactions, these membranes can undergo a transition to a crystalline monolayer that remains self-bound without external confinement. We further explore how the symmetries of the long-range interactions can be controlled through microwave dressing and discuss their consequences for the emerging phases of molecular ensembles. Our calculations enable direct comparisons with recent experiments and thereby provide a microscopic benchmark for our understanding of dipolar Bose–Einstein condensates.
Quantum fluctuations play a central role in the often exotic behavior of dipolar condensates. Yet, a consistent theoretical description of these fluctuations and their stabilizing effects in dipolar quantum gases has remained incomplete. We discuss the key conceptual challenges underlying such a theory and present a framework that addresses this long-standing problem. In particular, our approach goes beyond the commonly employed local-density approximation to the Lee–Huang–Yang (LHY) energy correction and enables a self-consistent determination of the equation of state. This makes it possible, for the first time, to determine the phase diagram of dipolar Bose–Einstein condensates within such a self-consistent framework and to resolve deviations between conventional LHY predictions and experimental observations.
