STUDY OF PHONON TRANSMISSION AT THE SOLID AND LIQUID INTERFACE OF ^3He

点击翻译按钮获取中文摘要

The sonic cell was designed and made, which bore under the ^3He melting pressure of 35 atm. ZnO is used as the transducer in the sonic cell. In order to increase transmission efficiency into ^3He, double layred anti-reflection coating is sputtered between the transducer and ^3He.First, we observed the propagation of zero sound in liquid ^3He down to temperature of about 2 mK at a frequency of 400MHz. This is the first observation of zero sound at the high frequency of 400MHz. In the 2mK temperature regime, the sound quanta has higher energy than thermal excitation energy so that the absorption of sound quanta takes place in the collisions of quasiparticles. According to Landau Ferimi liquid theory, the absorption in this regime is proportional to the square of frequency and independent of temperature. From our experimental result, the absorption is seen to remain finite at absolute zero temperature. The quantum limit of zero sound absorption is estimated to be observed.We observed sound propagation in solid ^4He as a test of our system. The sound signal propagating through solid ^4He increased inearly with input sound power in the low power regime. when the sound power was increased, nonlinear absorption occurred and the sound signal propagating through solid ^4He was saturated. This fact confirmed that ur system had enough sensitivity and power to observe sound propaation through solid He.We have tried to make solid and liquid interface between the transducer in our cell but it was hard to control and stabilize the interface. It has not been succeed to observe the sund signal which ropagates through or is reflected at the interface.