Quantum Institute: Visitor Schedule

The Quantum Lunch is regularly held on Thursdays in the Theoretical Division Conference Room, TA-3, Building 123, Room 121.
For more information, contact Diego Dalvit.

March 9, 2006
12:30 PM

Nikolay Prokofiev,
University of Massachusetts

How can superfluidity occur in a crystalline solid: He-4 superglass

Abstract

I will prove that the necessary condition for a crystal to be also a superfluid is to have zero-point vacancies, or interstitial atoms, or both, as an integral part of the ground state. As a consequence, in the absence of symmetry between vacancies and interstitials, superfluidity has zero probability to occur in commensurate solids which break continuous translation symmetry. I will discuss recent $^4$He experiments by Kim and Chan in the context of this theorem, question its bulk supersolid interpretation, and offer an alternative explanation in terms of the superfluid glass state or superfluid interfaces.