Phonon–phonon relaxation and thermoelectric effects in point contacts

The contribution of phonon-phonon scattering to point-contact thermoelectric effects (quenching of phonon drag thermo-emf and asymmetry in heat release in a symmetric point contact) is considered. The effective lengths of phonon relaxation due to normal processes lNc and umklapp processes lUc in the point contact are calculated for d≪lNc,lUc (d is the contact diameter). If the main relaxation mechanism is the nonelectron scattering of phonons of length lph, the quantities describing point-contact thermoelectric effects contain the parameter lph/lph-e (lph-e is the phonon-electron scattering length). However, the drag thermo-emf in a point contact and in a bulk conductor is not compensated completely as long as the electron transport in the point contact remains ballistic. The point-contact asymmetry of heat release Qa is also determined by the phonon scattering mechanism so that Qa ∼ min lph−ph,lph−e,dlph−e−1Qps (Qps is the asymmetry with dominating phonon-electron relaxation).

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