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Theory of plasmon‐assisted electron pairing in semiconductors
Author(s) -
Blank R.,
Haug H.
Publication year - 1995
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221880109
Subject(s) - plasmon , degenerate semiconductor , physics , plasma , electron , condensed matter physics , pairing , degenerate energy levels , excited state , plasma oscillation , semiconductor , atomic physics , quantum mechanics , superconductivity
Abstract It is shown that plasmon‐assisted superconductivity can occur in an electron plasma of a modulationdoped quantum well structure or in an optically excited, cool quasi‐equilibrium electron–hole plasma in stressed quantum wells. For our analysis the quasi‐classical approximation (QCA) for non‐equilibrium Keldysh‐Green functions for carriers of a degenerate plasma is used. The screening is described in RPA, simplified further for some of the calculations by a damped plasmon‐pole approximation (PPA). Because the plasmon coupling is strong the appropriately modified Eliashberg equations are derived and analyzed for the complex frequency‐dependent normal and anomalous self‐energies. The plasmon frequency in a semiconductor plasma with a typical density of 10 18 cm −3 is of the order of some 10 meV. If the spectral density of the plasmon is not too broad, a pairing instability is found also in the range of interparticle distances with r s < 1, where QCA and RPA are valid. Depending on the material, transition plasma temperatures of up to 30 K are obtained which can be enhanced further by quantum confinement and special properties of the band structure. The underlying virtual exchange of plasmons can only be obtained in a fully dynamical description, and is absent in the commonly used quasi‐static quasi‐particle approximations.