包括扩散模式的Andreev-Lifshitz超固体流体力学
Andreev-Lifshitz Supersolid Hydrodynamics Including the Diffusive Mode
摘要：
我们重新研究了Andreev-Lifshitz的超固体理论。该理论隐含地忽略了改变空位数的均匀体过程，并且假设除了晶格应力$λ_{ik}$之外还有内部压力$P$。$P$和$λ_{ik}$中的每一个占据外部或施加的压力$P_a$的一部分（对于固体4He是必需的）。该理论给出了四对传播的弹性模式，其中一对对应于第四声模式，和一个单一的扩散模式，这是以前没有分析过。扩散模式有三个不同的速度，超流速度比正常的流体速度大得多，这反过来又比晶格速度大得多。模式结构取决于某些动力学系数和热力学导数的相对值。我们考虑在固体4He在低温下的加压实验中，根据这种扩散模式和以前的分析模式在一个正常的固体没有超流成分。
英文摘要：
We have re-examined the Andreev-Lifshitz theory of supersolids. This theory implicitly neglects uniform bulk processes that change the vacancy number, and assumes an internal pressure $P$ in addition to lattice stress $λ_{ik}$. Each of $P$ and $λ_{ik}$ takes up a part of an external, or applied, pressure $P_a$ (necessary for solid 4He). The theory gives four pairs of propagating elastic modes, of which one pair corresponds to a fourth-sound mode, and a single diffusive mode, which has not been analyzed previously. The diffusive mode has three distinct velocities, with the superfluid velocity much larger than the normal fluid velocity, which in turn is much larger than the lattice velocity. The mode structure depends on the relative values of certain kinetic coefficients and thermodynamic derivatives. We consider pressurization experiments in solid 4He at low temperatures in light of this diffusion mode and a previous analysis of modes in a normal solid with no superfluid component.
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