Multiband superconductivity with competing intra- and interband pair channels

In multiband superconductivity interband interaction channels creating the pairs of intraband [Formula: see text] and interband [Formula: see text] compositions can appear. Simultaneous functioning of these channels is investigated here. A three-band model where two similar bands [Formula: see text] interact with the itinerant-band has been proposed. The mean field Hamiltonian incorporates three order parameters [Formula: see text]; [Formula: see text]; [Formula: see text] genetically associated with dispersive bands. Calculated quasiparticle energies and operator averages lead to a coupled nonlinear equation system for the order parameters. Illustrative calculations versus temperature have been made for overlapping bands. At fixed parameters, the basic system has two independent solutions. The free energy has a complicated structure of extremal points. The interaction of channels with intra- and interband points is seen. These channels compete in general. From the point where the gap, type parameters associated with one channel become zero, the other continues as the first channel was logged out. The general behaviour of order parameters distribution is very sensible to [Formula: see text]. Events of critical nature appear. Weakening of [Formula: see text] stimulates the formation of closed bubbles built up by the same type parameters from different parallel solutions.

Hole intersubband transitions in wurtzite and zinc-blende strained AlGaN/GaN quantum wells and its interband interaction dependence

Valence intersubband transitions of the wurtzite (WZ) strained AlGaN/GaN quantum wells are examined theoretically and compared with those of the zinc-blende (ZB) ones. In particular, the effect of the interband interaction between conduction (CB) and valence (VB) bands has been taken into account explicitly. We have used the 8-bands k.p model for both WZ and ZB structures to calculate subband energies and wavefunctions of Al 0.3 Ga 0.7 N/GaN quantum wells (QWs). The results indicate that, the prominent transitions for both ZB and WZ QWs were found to be essentially related to the heavy- and light-hole subbands. For the x-polarization, we have shown that it is necessary to take into account explicitly the interband interaction between CB and VB. Finally, we can predict that WZ QWs are more convenient than ZB QWs in most applications involving intersubband transitions, especially for the z-polarized light.

The Critical Temperature of Two-Band Superconductors with Pseudogap

The exact formula of Tc’s equation of two-band s-wave superconductors with Pseudogap in weak-coupling limit are derived by considering the influence of interband interaction. The pairing interaction in each band consisted of 2 parts the electron-phonon interaction and non-electron-phonon interaction are included in our model. It was found that the critical temperature is increased as Pseudogap, phonon coupling of 1st band constant and interband phonon coupling constant increased.

INTEGRABLE TWO-PARAMETER MODEL OF THE FERMI GAS

We present a two-band model of the gas of fermions consisting of a parabolic band of conduction electrons and a band of local pairs interacting via a δ-function interband interaction. The model is integrable and its solution has been obtained by means of the Bethe ansatz. The ground state energy and the density of conduction electrons have been calculated numerically.