Anisotropical glassy properties--a theoretical model*

We apply the model introduced in Phys. Rev. B {\bf 75}, 064202 (2007), to calculate the anisotropy effects in the interaction of two level systems with phonons and elastic waves in disordered crystals. In this model, the interaction strength depends on the orientation of the TLS with respect to the strain field through a $6\times6$ symmetric tensor of deformation potential parameters, $[R]$. The structure of $[R]$ is similar to the structure of the tensor of elastic stifness constants, in the sense that they are determined by the same symmetry transformations. In this way, we emphasize the anisotropy of the interaction of elastic waves with the ensemble of two-level systems in disordered crystals. We also point to the fact that the ratio $\gamma_l/\gamma_t$ has a much broader range of allowed values in disordered crystals than in isotropic solids. \\[4pt] {\bf Related publications:}\\ [0pt] [1] D. V. Anghel and D. Churochkin, Europhys. Lett. {\bf 83}, 56004 (2008).\\[0pt] [2] D. V. Anghel and D. Churochkin, Phys. Rev. B {\bf 78}, 094202 (2008).