My first session was on supersolid He-4, up bright and early for the 8am start. The paper under discussion for the first talk appeared in Nature last year by Xi Lin and colleagues from Penn State University. They looked at the heat capacity of He-4 at low temperature (T < 0.5 K), and reported a peak centered around T = 0.08K.

It also became apparent the difficulties of making accurate measurement at such temperatures, they reported that they constructed 20 low temperature cells for the measurement, and only one of them was heat leak proof.

A large question in the area of supersolid He-4 is what the role of He-3 impurities are, in the final talk of the session given by Philip Anderson this question seems to have even got the better of the Nobel prize winner himself, when he openly admitted to not knowing the answer.

The supersolid peak is independent on the amount of He-3 impurities with Lin presenting samples with 0.3 ppm (parts per million) and 1ppb (parts per billion) of He-3 impurity. But the peak did slightly decrease in temperature when the samples was annealed for longer, so it seemed to depend on how the sample is made. A comment was later made that the supersolid peak could be intimately linked with disorder.

Unfortunately the session did break up a little when the second speaker didn’t show up – which was supposedly a knock on effect from the storm that was over the east coast at the weekend.