Topic: "Dissipative Mysteries-Experiments on Glasses at Low Temperatures" (Video)
Abstract: I will discuss two recent experiments on glasses at Cornell. The first shows signatures (in the acoustic response) for the presence of interactions between two level systems that comprise the "building blocks" of glasses. The temperature dependence tracked down to below 3 mK shows a linear T behavior in dissipation (in contrast to the T3 behavior predicted by the standard tunneling model). The second examines a disordered material (silicon nitride) that incorporates a high internal stress and that displays extraordinarily high Qs at room temperature and down to the "plateau" region between 0.1 and 10K, where it is found that almost all glasses show a dissipation that is on the order of 3_10-3. High stress nitride deviates from this behavior displaying a dissipation that is almost 1000 _ smaller. Stress relieved structures (cantilevers) fabricated from the same material show a dissipation in closer agreement to the universal behavior. Future work will be discussed.