Is a supersolid still out there?

Is a supersolid still out there?
Prof. John Reppy, Dept of Physics, Cornell University
Date and time: Thu, Nov 17, 2016 - 11:30am
Location: LGRT 1033
Category: Condensed Matter Seminar
Abstract:
After almost a decade of experiments attempting to display a superfluid-like behavior in solid 4He, it now seems that this "super-solid" state may not exist. Although, the results of some of the experiments reporting a supersolid behavior can be interpreted by other means, there exist others for which a plausible alternative explanation is lacking. Currently we are performing experiments employing a double torsional oscillator (TO), which can discriminate between two scenarios - that of signals arising from the acceleration of the sample involving elastic effects, which will depend on the square of the frequency, and that of a supersolid condensate indicated by a frequency-independent term. We see a small frequency-independent term for our bulk samples contained in both cylindrical and annular geometries. This term represents a fraction of about 10-4 of the total moment of inertia of the solid sample. The observation of such small signals requires a high degree of stability for the TO and in our most recent measurements, we have been able to improve the stability and signal to noise ratio by an order of magnitude over our previous work. The small remaining frequency-independent signals, we observe, are difficult to explain by elastic effects alone and may be a sign that supersolidity still exists.