Boson wavefunction and condensation energy in the superconducting state of doped semiconductors

摘要

The superconducting state of doped semiconductors, in which a superconducting gap opens in the spectrum of one-particle states formed (upon doping) in the region of the initial energy gap, is studied within the framework of the Holstein-Anderson model. The wavefunction of the relative motion of a pair of particles in the bound state is determined. The dependence of the size of this wavefunction on the level of doping in the overdoping region of the phase diagram is consistent with the published experimental data for La2-xSrxCuO4. Variation of the temperature in the range of T < T-c only influences the natural normalization of the boson wave-function (normalized to the boson density), while the size of the wavefunction is independent of the temperature. Theoretical values of the condensation energy and the heat capacity jump upon the superconductor-metal transition in the region of optimal doping agree with the experimental data for La2-xSrxCuO4.