The effect of radiation on the electron pairing in a multiband system

Abstract

The possible occurrence of a generalized (l-wave) nonequilibrium superconducting state in a multiband system under certain conditions is studied. In the model the radiation field causes interband mixing, and phonons of an appropriate mode (branch) are involved in the interband scattering of electrons of two conduction bands of the system. The strength of the generalized l-wave pairing interaction between quasiparticles belonging to new radiation admixed states depends on the density (n₀/V) of quanta in the system. The coupling constant has the form λ₁=A₁B(n₀/V)/[C+B (n₀/V)], where A₁, B, and C are parameters. For C > B(n₀/V), the transition temperature T₁^∗ increases with (n₀/V) in the initial stages. It levels off with higher power. With further increase of power, the transition temperature is expected to drop sharply due to heating effects which cause pair breaking. Estimates show that p-wave (triplet state) pairing may be possible under radiation-induced nonequilibrium situations in appropriate systems. Estimates for lifetimes of various processes (quasiparticle, phonon, pair relaxation, and photon-induced mixing) show that the coherence required for the mixing and pairing effects will be maintained for the temperature range and photon density considered.