Model For Conduction Electrons Research Articles

Anisotropy of Gap Parameter in Cuprate Superconductors

The anisotropy of gap parameter in cuprate superconductors is explained in the frame work of BCS theory using two-dimensional itinerant model of conduction electrons. The BCS gap equation at T = 0 is solved in the first iteration approximation. The two-dimensional electron energy bands and electron-phonon interaction in tight-binding approximation are used. The explicit expression for the gap parameter Δ°(k) is evaluated for the Einstein model of the solid. It is found that Δ°(k) consists of a constant part and an oscillatory part which varies as sin 2 k x a. The magnitude of oscillatory part is found to depend upon the cutoff energy hw c , width of the singularity in the density of states near Fermi surface and overlap integral.

Observation of diffusion of H and D on Ni(111) from over-barrier hopping to nonactivated tunneling.

We measured the diffusion coefficients for hydrogen (H) and deuterium (D) on Ni(111) from 108 to 154 K. We observed nonactivated tunneling following thermally activated hopping at around 125 K for both isotopes. The nonactivated tunneling rates show weak isotope dependence. Our observation confirms an early report by Lin and Gomer [Surf. Sci. 225, 41 (1991)]. The nonactivated tunneling is analyzed with both a modified polaron model, which includes adatom-phonon couplings varying quadratically in phonon coordinates, and the conduction electron model. The weak isotope dependence is understood as a result of a large WKB tunneling matrix element on Ni(111).

Five-level k · p model for conduction electrons in GaAs. Description of cyclotron resonance experiments

Five-level k·p model for the conduction electrons in GaAs in the presence of a quantising magnetic field is developed and used to describe spin splittings of the cyclotron resonance and the donor-shifted cyclotron resonance peaks, observed in this material up to fields of 22.5 T. It is shown that the spin splittings are insensitive to polaron effects and that their values can be very well described by the model. Required band parameters correctly account for the rate of electron spin relaxation in GaAs due to inversion asymmetry, as determined by other authors.

The Ruderman-Kittel-Kasuya-Yosida Interaction on Conduction Electrons Having the Brillouin Zone Boundary

The modified Ruderman-Kittel-Kasuya-Yosida exchange constant J ( Q ) of local magnetic moment interacting via the conduction electrons having energy gap at the Brillouin zone boundaries is expressed through the use of the state density and the susceptibility function of these electrons. The effects of the Brillouin zone boundary appear specially on J (0). A simple band model of conduction electrons with {100} boundaries is considered as an example. On this model, we show that the positive peak of the J (0) curve plotted against the conduction electron number n shifts, with the change of the energy gap at the boundary, to the value of n where the Fermi surface starts to fill outside the Brillouin zone boundary. We can understand on this model, for example, the change of sign of θ p observed in rare earth intermetallics with Mg having the CsCl structure by taking the suitable OPW potentials for these compounds.

Fluctuations in simple mechanical models

Synopsis The considerations of the statistical aspect of the second law of thermodynamics of a previous paper are extended. The influence of fluctuations in a class of simple models is investigated generally, and expressions found for the mean life and average time of recurrence of non-equilibrium states which agree with previous results. The models include the Lorentz model of conduction electrons in a metal and the Ehrenfest wind-wood model. The results are used to illustrate the time behaviour of an ensemble of such systems.