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摘要
Observations have been made to reveal unusual aging behavior in solid He-4 samples contained in a torsional oscillator. Oscillation of samples is initiated at a given oscillator drive amplitude near 100 mK. After the samples are cooled to a measurement temperature, they are "aged" for a waiting time, t(w), between 15 min and 25 h. The drive amplitude is then halved and subsequent variation in the oscillator response amplitude, A(t), and frequency are monitored as time t elapses. When the measurement temperature is lower than T-s = 40 mK, A(t) shows unusual behavior: A(t) initially undershoots to less than half of the original value, partially recovers exponentially and eventually continues to increase logarithmically. The amount of undershoot, partial recovery magnitude and the rate of logarithmic increase all show aging effect with logarithmic dependence on t(w). When the measurement temperature is greater than T-s, the above unusual behavior in A(t) disappears. If solid He-4 cooled below T-s behaved analogously to spin glasses, A(t/t(w)) would be independent of t(w). Such behavior of A(t/t(w)) is not observed. Origin of the unusual aging behavior in solid He-4 is not yet clear. Motion of dislocation lines is discussed as a possible origin.
- 出版日期2013-10
