Thomas Bland (Institute for Quantum Optics and Quantum Information, Innsbruck) gives a webinar on “Two dimensional supersolidity in a circular trap”.

Dipolar condensates have recently been coaxed into supersolid phases supporting both superfluid and crystal excitations. While the first dipolar supersolids consisted of one dimensional (1D) droplet arrays, an experiment has now achieved two dimensional (2D) supersolidity. We theoretically explore the role of dimensionality, ranging from 1D to zigzag, through to 2D supersolids in circular traps. We predict that 2D supersolids may be as favorable as their 1D counterparts, provided that one scales the atom number to the trap volume. While 1D supersolids may be prepared from condensates via a roton instability, such a procedure in 2D tends to destabilize the supersolid. The 2D roton modes have little in common with the supersolid configuration – instead, unstable rotons produce a small number of central droplets, which triggers a nonlinear process of crystal growth. We calculate excitations for a 2D supersolid ground state, and make comparisons with 1D arrays using the static structure factor. By evaporatively cooling directly into the supersolid phase – hence bypassing the first-order roton instability – we experimentally produce a 2D supersolid in a near-circular trap.