Novel Behavior in Solid
4He: New Tricks in an Old Dog
Robert Hallock
In the early
1970’s it was predicted that solid helium might display some unusual
superfluid-like behavior. Several years ago interest in the behavior of
solid 4He was rekindled, first by John Goodkind's
group and shortly later in a more dramatic fashion by Eunseong
Kim and Moses Chan who showed that when solid helium was put into rotation some
of it seemed to be left behind. Indeed, solid helium has over the past
few years shown a variety of very unusual, even surprising, phenomena. Some of
these will be briefly reviewed and then experiments that demonstrate the
transmission of atoms through the solid in response to an applied chemical
potential difference, which may deepen the mystery about the solid, will be
described in more detail.