Now published in the journal “Physical Review A”! The newest work from the Theory group are the results of PhD student Elena Poli’s DK-ALM research stay abroad in the group of Professor Blair Blakie at the University of Otago, NZ. In this theory paper, they study the excitations and elastic parameters of the 2D supersolid state of a BEC with dipolar interactions and soft-core interactions. See the following excerpt from the abstract for some of the details of this collaborative effort:
[The] supersolid state has three gapless excitation branches arising from the spontaneously broken continuous symmetries. Two of these branches are related to longitudinal sound waves, similar to those in one-dimensional supersolids. The third branch is a transverse wave arising from the non-zero shear modulus of the two-dimensional crystal. We present the results of numerical calculations for the excitations and dynamic structure factor characterising the density fluctuations, and study their behavior across the discontinuous superfluid to supersolid transition. We show that the speeds of sound are described by a hydrodynamic theory that incorporates generalized elastic parameters, including the shear modulus. Furthermore, we establish that dipolar and soft-core supersolids manifest distinct characteristics, falling into the bulk incompressible and rigid lattice limits, respectively.
See the article in PRA here: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.053301
See the pre-print here: Excitations of a two-dimensional supersolid https://arxiv.org/abs/2407.01072.