Evidence for a Superglass State in Solid 4 He

Abstract

Glasslike Supersolid Recent experiments with solid helium confined to the ring of a torsional oscillator at extremely low temperatures have been interpreted in terms of an exotic supersolid phase—a crystalline solid that somehow flows like a superfluid. However, behavioral differences between samples have raised many questions (see the Perspective by Saunders ). Hunt et al. (p. 632 ) present a comprehensive study of the relaxation dynamics of the torsional oscillator system as a function of time and temperature. The data provides evidence for a “supersolid glass,” where glassy behavior of crystal dislocations and superfluidity can coexist. In a separate theoretical study, Anderson (p. 631 ) argues that supersolidity ought to be a ground state for all bose solids, but that defects in the sample may mask the supersolid signature.