Supersolidity in Dipolar Bose-Einstein condensates

IQOQI Quantum Seminar

Abstract: What happens when a solid starts flowing like a superfluid, yet still creaks like a crystal? This is the remarkable behaviour of a supersolid — a phase of matter that combines crystalline order with frictionless flow. Once a long-standing theoretical curiosity, supersolidity has now been realised in an exceptionally clean and tunable platform: dilute dipolar Bose–Einstein condensates of highly magnetic atoms such as dysprosium and erbium. Recent experiments have used the competing effects of short-range contact and long-range dipolar interactions to self-organise these ultracold gases into periodic density modulations, while maintaining global phase coherence.

In this talk, I’ll discuss two-dimensional dipolar supersolids, examining the ground state phase diagram and excitations. Due to the broken gauge and translational symmetries, these supersolids exhibit three gapless excitations branches with associated speeds of sound. I will discuss the application of hydrodynamic theories to describe the supersolid properties and relate the speeds of sound to its elastic parameters. I will also explore some examples of nonequilibrium dynamics.

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