Supersolid phases of bosonic particles in a bubble trap

Confinement can have a considerable effect on the behavior of particlesystems, and is therefore an effective way to discover new phenomena. A notableexample is a system of identical bosons at low temperature under an externalfield mimicking an isotropic bubble trap, which constrains the particles to aportion of space close to a spherical surface. Using Path Integral Monte Carlosimulations, we examine the spatial structure and superfluid fraction in twoemblematic cases. First, we look at soft-core bosons, finding the existence ofsupersolid cluster arrangements with polyhedral symmetry; we show how differentnumbers of clusters are stabilized depending on the trap radius and theparticle mass, and we characterize the temperature behavior of the clusterphases. A detailed comparison with the behavior of classical soft-coreparticles is provided too. Then, we examine the case, of more immediateexperimental interest, of a dipolar condensate on the sphere, demonstrating howa quasi-one-dimensional supersolid of clusters is formed on a great circle forrealistic values of density and interaction parameters. Crucially, thissupersolid phase is only slightly disturbed by gravity. We argue that thepredicted phases can be revealed in magnetic traps with spherical-shellgeometry, possibly even in a lab on Earth. Our results pave the way for futuresimulation studies of correlated quantum systems in curved geometries.