Sound conversion in impure superfluids
Sound conversion in impure superfluids
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不纯超流体中的声音转换
DOI：
10.1103/physrevb.63.140507
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发表时间：
2001
影响因子：
3.7
通讯作者：
G. Lawes
中科院分区：
文献类型：
--
作者：
P. Brusov;J. Parpia;P. Brusov;G. Lawes
我们考虑了在不同的不纯超流系统中第一声到第二声的转换以及相反的转换。我们计算温度~熵之间的耦合！振荡和压力~密度！不纯超流体的振荡~包括He-He混合物！以及气凝胶中的超流He（He和He），并表明这些系统中的声转换由c（]r/]c）或由srars（而不是]r/]T）控制，而在纯He中，[r/]T非常小。这种置换在不纯超流体和气凝胶超流体中的声转换现象中起着重要作用。它增强了两种声音的耦合强度，降低了均匀超流体中非线性过程的阈值。气凝胶中超流He和He的慢模，气凝胶中HeII的热脉冲以第一声速传播等现象可理解为双声转换现象。
We consider the conversion of first sound into second sound and the reverse in different impure superfluid systems. We calculate the coupling between temperature ~entropy! oscillations and pressure ~density! oscillations for impure superfluids~including He-He mixtures! and for superfluid He~both He and He) in aerogel and show that sound conversion in these systems is governed by c(]r/]c) or by srars ~instead of ]r/]T, which is enormously small in pure He !. This replacement plays a fundamental role in the sound conversion phenomenon in impure superfluids and superfluids in aerogel. It enhances the coupling strengths of the two sounds and decreases the threshold values for nonlinear processes in homogeneous superfluids. Some phenomena such as the slow mode of superfluid He andHe in aerogel, and heat pulse propagation with the velocity of first sound in HeII in aerogel can be understood as a double sound conversion phenomena.