Observation of Temperature Chaos in Mesoscopic Spin Glasses

Temperature Chaos (TC) results from a change in temperature for spin glasses (SG), polymers, and other glassy materials. When the temperature is changed, TC means that the new state has no memory of the preparation of the initial state. TC was predicted long ago [PRL {\bf 48}, 767 (1982)]. However, ``An experimental measurement of TC is still missing" [EPL {\bf 103}, 67003 (2013)]. One reason for this is the question of length scale. In the thermodynamic limit, even an infinitesimal temperature change, $\Delta T$, will create a chaotic condition. However, by working at the mesoscale, one can establish a length scale sufficiently small to exhibit reversible behavior before crossing over to chaotic behavior as the temperature change increases. Observation of TC is possible because, on reasonable laboratory time scales, the SG correlation length can grow to the size of the thickness of the film, $L$. The lower critical dimension for a SG is $\sim 2.5$, so that the thin film SG crosses over to a glass temperature $T_g=0$. However, there remains quasi-equilibrium SG states with length scales $