Metallic point contacts in a pseudoballistic regime. Phonon generation and electron drag

The generation of nonequilibrium phonons and electron entrainment by a phonon flow are studied in metallic point contacts with a strong phonon–electron interaction. This situation, corresponding to the condition lph-e ≪ d ≪ le-ph (lph-e , le-ph are the lengths of the phonon–electron and electron–phonon scattering, d is the contact diameter), is tentatively called a pseudoballistic regime. At d ∼ 10−5 − 10−4 cm this regime can set in the point contact at nitrogen temperatures. It is shown that in contacts of this kind, asymmetric phonon generation occurs leading to a temperature difference ΔT(V) between the contact banks which is nonlinear with respect to the applied voltage V. Unlike the case of the ballistic phonon transport (d ≪ lph-e), the ΔT(V) value does not contain the small parameter d/lph-e. There is no complete compensation of the entrainment thermo-emf of the contact Scph and bulk metal Smph, if the momentum length of electron scattering exceeds d. This is proposed as a possible explanation of experimental results on the temperature dependence of Smph−Scph at T ∼ 100 K.

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