The Supersolid Phase of Helium-4: to flow or not to flow?

by Prof. Matthias Troyer (ETH-Switzerlad)

Tuesday 10 Feb 2009, 16:00 → 18:00 Europe/Rome

Aula Conversi (Dip. di Fisica - Edificio G. Marconi)

Can a solid be superfluid? At first sight the answer is an obvious "no". Solid and superfluid phases properties are as contradictory as anything in Nature. Nevertheless there have been speculations for more than half a century years, whether quantum mechanics can stabilize a "supersolid" phase, a solid crystal exhibiting non-dissipative superflow. While this phase has eluded detection for 50 years, first experimental evidence has recently been found in experiments by Kim and Chan. In this talk I will review the experimental evidence and controversies around the supersolid phase of Helium and present our ab- initio quantum Monte Carlo simulations of the superfluid properties of solid Helium. While a perfect Helium single crystal is an insulator, any Helium solid occurring in Nature is imperfect, and it is just these crystal defects that allow superflow in solid Helium.