Phonon Dissipation Research Articles

Model for phononic energy dissipation in friction

We have developed a microscopic model of phononic energy dissipation in friction that involves the generation of a local excess phonon distribution in a nanoparticle between two sliding objects, and its damping into the objects. The conversion of the energy stored in the nanoparticle into excess phonons and their decay rates are calculated. The model can be extended to include randomly distributed nanoparticles and phonon-phonon interaction through anharmonic couplings. By using this model we present a quantitative analysis of energy dissipation in sliding friction.

Peculiarities of acoustic energy transmission from liquid helium to metals: A Review

Experimental and theoretical studies of the coefficient α of phonon energy transmission from liquid helium to cubic-symmetry metals (tungsten, copper, and aluminum single crystals and gold polycrystals) are reviewed briefly. It is shown that the transmission coefficients for single crystals with a perfect surface are correctly described by the theory of acoustic impedance mismatch model, taking into account absorption of phonons by conduction electrons. Andreev’s theory of electron resonant absorption of a Rayleigh wave by the surface of single crystal with α∼1 is confirmed. In a strongly anisotropic copper single crystal, a resonant pseudo-surface wave absorption peak is also observed. It is shown for aluminum that phonon dissipation decreases sharply upon a transition from the normal to superconducting state, and the height of the Rayleigh peak decreases accordingly. It is found that the main mechanism of phonon scattering in a polycrystal is the Rayleigh scattering at grain boundaries, which is proport...

Intersubbands carrier dynamics in quantum wire structures

We report new fundamental results on carrier transport in quantum wire structures. In the extreme quantum limit, “low” field transport characteristics show mobility enhancement associated with anomalous carrier cooling due to quenching of electron-electron interaction and strong optic phonon dissipation. In condition of resonance between the optic phonon energy and the electronic subband separation, a substantial population inversion between adjacent off-resonance subbands arises as a natural consequence of optic phonon absorption in confined ID systems. Radiative far infra-red emission induced by this new “phonon pumping” mechanism are subject to selection rules but theoretical estimations of the gain coefficient for stimulated emission are encouraging. In high field transport, simulation shows rapid carrier escape from quantum wires caused by intervalley scattering and real space transfer.

Dynamics of physisorption for the H 2,D 2Cu(100) and H 2Ag(111) systems

We have performed detailed semiclassical stochastic trajectory, classical trajectory and exact quantal calculations on H 2 and D 2 collisions with Cu(100) using two different interaction potentials. The first is weakly anisotropic while the second is as anisotropic as possible without violating the free rotational motion of H 2 at the equilibrium distance for physisorption. Energy transfer to phonons was modelled within the semiclassical stochastic trajectory method using the generalized Langevin equation approach. Energy transfer to electron-hole pairs was incorporated via an electronic friction coefficient, using two different parametrized forms, one of which gives strong friction and the other weak. Our results can be summarized as follows for the Cu(100) system: (1) Even for the very anisotropic potential, trapping via translational to rotational energy conversion does not occur to any significant degree. (2) The dependence of the sticking coefficient on the rotational level, j, is negligible for both potentials, irrespective of whether energy is transferred to phonons and/or electron-hole pairs. (3) The sticking coefficient depends strongly upon the orientation state, m, of the rotor for the strongly anisotropic potential. (4) The magnitude of the sticking coefficient varies from 0.03–0.1 for H 2Cu and 0.06–0.11 for D 2Cu, with the lower numbers appropriate for the phonon mechanism and the upper for both phonons and (strong coupling to) electron-hole pairs. (5) The ratio of sticking coefficients for D 2 and H 2 is ≈1.8 for phonon dissipation and ≈1.0 for both phonon and (strong coupling to) electron-hole pair dissipation. Fewer results for the H 2Ag(111) system are reported but these are in qualitative accord with the H 2Cu(100) features. The magnitude of the sticking coefficient is smaller for H 2Ag than for H 2Cu.

A dissipative trajectory theory for reactive scattering at surfaces

The Tully-Preston “surface-hopping trajectory model” originally constructed for gas phase reactive-scattering events is adapted to a class of atomic scattering processes at solid surfaces involving a substrate-induced diabatic transition on the incident atom. The role of energy dissipation due to substrate excitations is shown to drastically influence the reaction probability. Within the context of the trajectory theory, dissipation places upper limits on the number of trajectories leading to non-reactive events and hence on the reaction probability. This is illustrated by example, using sticking as a prototypical event. A criterion for large sticking coefficients is given in terms of vibrational frequencies and linewidths and of desorption energies, all quantities being experimentally accessible with current state-of-the-art measurement techniques. An experiment, based on the present theory, is proposed which could differentiate between electronic and phonon dissipation.

Electron-phonon (trapped photon) coupling and infrared coaxial transmission line theory of energy transport in mitochondria and nerve.

This paper develops quantitatively for the kinetics of mitochondrial oxidation the implications of the hypothesis that phosphorylation is accomplished by phonons in the mitochondrial solid. The concept is used that the phonon acts like a trapped photon to produce a reverse photocurrent, which inhibits oxidation, in the absence of phonon dissipation due to phosphorylation or uncoupling. The same concept in reverse is shown to explain qualitatively the generation of membrane potentials in nerve axon. Infrared optical phonons generated in the above processes are expected to have limited mobility, but it is shown that the structure and geometry of the lipid bilayer membrane are well adapted to the rapid and efficient dissemination of this energy throughout the mitochondrion or nerve axoni n the form of infrared electromagnetic waves by a coaxial transmission line mechanism. The mitochondrion may act like an infrared coaxial resonant cavity.