The effect influence of elastic energy anisotropy on the mutual drag of electrons and phonons and the electrical resistance of potassium crystals at low temperatures have investigated. We have analyzed the momentum exchange between the electron and three phonon flows corresponding to three branches of the vibrational spectrum in the hydrodynamic approximation. The actual mechanisms of phonon momentum relaxation have taken into account: scattering at sample boundaries, dislocations, and in the processes of phonon-phonon transfer. It have shown that in the limiting case of strong mutual drag of electrons and phonons, the electrical resistance will be much lower than that given by the Bloch–Grüneisen theory, and the phonon and electron drift velocities are close and they are determined by the total phonon relaxation rate in resistive scattering processes. In the opposite case, when resistive scattering processes dominate for phonons and the phonon system remains in equilibrium, then the electrical resistance follows the Bloch–Grüneisen theory. In this case, the drift velocities of all modes are different and much less than the electron drift velocity.

Исследовано влияние фокусировки фононов на фононный транспорт в полупроводниковых и диэлектрических кристаллах с различным типом анизотропии упругой энергии при низких температурах. Рассчитаны эффекты МакКарди в теплопроводности упруго анизотропных кристаллов в режиме кнудсеновского течения фононного газа. Проанализировано влияние фокусировки фононов на распространение и граничное рассеяние фононов в образцах с квадратным и прямоугольным сечениями, и дано физическое объяснение эффектам МакКарди.

Phonon pulse propagation in cubic crystals with different elastic energy anisotropy types is considered. A closed analytical expression is derived for the phonon flux enhancement factor. The features of its dependences on the isoenergetic surface curvature types are analyzed for all acoustic modes and anisotropy parameter values and signs.