Dissipative mysteries -- experiments on glasses at low
temperatures
Jeevak Parpia
Department of Physics,
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.