| 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 will explore the curious world of two-dimensional dipolar supersolids. These quantum materials break multiple symmetries and exhibit up to 3 different types of sound-wave excitations. Interestingly, this quantum fluid develops a shear-modulus marking solid-like rigidity, and exhibits transverse sound waves. I will discuss the underlying theory for the ground states and excitations, and how long-wavelength properties can be described by a hydrodynamic theory that incorporates both elasticity and superfluidity. |
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