Within the framework of compact density matrix approach and iterative procedure, a detailed procedure for the calculation of the second-harmonic generation (SHG)susceptibility tensor is given in the electric-field-bia...Within the framework of compact density matrix approach and iterative procedure, a detailed procedure for the calculation of the second-harmonic generation (SHG)susceptibility tensor is given in the electric-field-biased parabolic and semi-parabolic quantum wells (QWs). The simple analytical formula for the SHG susceptibility in the systems is also deduced. Numerical results on typical AlGaAs/GaAs materials show that, for the same effective width,the SHG susceptibility in semi-parabolic QW is larger than that in parabolic QW due to the self-asymmetry of the semiparabolic QW, and the applied electric field can make the SHG susceptibilities in both systems enhance remarkably.Moreover, the SHG susceptibility is also related to the parabolic confinement frequency and the relaxation rate of the systems.展开更多
By using determinant method as in our recent work, the IO phonon modes, the orthogonal relation for polarization vector, electron-IO phonon F^6hlich interaction Hamiltonian, the dispersion relation, and the electron-p...By using determinant method as in our recent work, the IO phonon modes, the orthogonal relation for polarization vector, electron-IO phonon F^6hlich interaction Hamiltonian, the dispersion relation, and the electron-phonon coupling function in an arbitrary layer-number quantum well system have been derived and investigated within the framework of dielectric continuum approximation. Numerical calculation on seven-layer AlxGal-xAs/GaAs systems have been performed. Via the numerical results in this work and previous works, the general characters of the IO phonon modes in an n-layer coupling quantum well system were concluded and summarized. This work can be regarded as a generalization of previous works on IO phonon modes in some fLxed layer-number quantum well systems, and it provides a uniform method to investittate the effects of IO phonons on the multi-layer coupling quantum well systems.展开更多
Under dielectric continuum approximation,interface optical (IO) phonon modes and the Froehlich electron IO phonon interaction Hamiltonian in a multi-shell spherical nanoheterosystem were derived and studied.Numerical ...Under dielectric continuum approximation,interface optical (IO) phonon modes and the Froehlich electron IO phonon interaction Hamiltonian in a multi-shell spherical nanoheterosystem were derived and studied.Numerical calculations on three-layer and four-layer CdS/HgS spherical nanoheterosystems have been performed.Results reveal that there are four IO Phonon modes for the three-layer system and six IO phono modes for the four-layer system.On each interface,there are two IO phonon modes,the frequency of one is between wTO,CdS and ωLO,CdS,and that of the other is between ωTO,HgS and ωLO,HgS.With the increasing of quantum number l,the frequency of each IO mode approaches one of the two frequency values of the single CdS/HgS heterostructure,and the potential for each IO mode is more and more localized at a certain at a certain interface,furthermore,the coupling between the electron-IO phonos becomes weaker.展开更多
文摘Within the framework of compact density matrix approach and iterative procedure, a detailed procedure for the calculation of the second-harmonic generation (SHG)susceptibility tensor is given in the electric-field-biased parabolic and semi-parabolic quantum wells (QWs). The simple analytical formula for the SHG susceptibility in the systems is also deduced. Numerical results on typical AlGaAs/GaAs materials show that, for the same effective width,the SHG susceptibility in semi-parabolic QW is larger than that in parabolic QW due to the self-asymmetry of the semiparabolic QW, and the applied electric field can make the SHG susceptibilities in both systems enhance remarkably.Moreover, the SHG susceptibility is also related to the parabolic confinement frequency and the relaxation rate of the systems.
文摘By using determinant method as in our recent work, the IO phonon modes, the orthogonal relation for polarization vector, electron-IO phonon F^6hlich interaction Hamiltonian, the dispersion relation, and the electron-phonon coupling function in an arbitrary layer-number quantum well system have been derived and investigated within the framework of dielectric continuum approximation. Numerical calculation on seven-layer AlxGal-xAs/GaAs systems have been performed. Via the numerical results in this work and previous works, the general characters of the IO phonon modes in an n-layer coupling quantum well system were concluded and summarized. This work can be regarded as a generalization of previous works on IO phonon modes in some fLxed layer-number quantum well systems, and it provides a uniform method to investittate the effects of IO phonons on the multi-layer coupling quantum well systems.
文摘Under dielectric continuum approximation,interface optical (IO) phonon modes and the Froehlich electron IO phonon interaction Hamiltonian in a multi-shell spherical nanoheterosystem were derived and studied.Numerical calculations on three-layer and four-layer CdS/HgS spherical nanoheterosystems have been performed.Results reveal that there are four IO Phonon modes for the three-layer system and six IO phono modes for the four-layer system.On each interface,there are two IO phonon modes,the frequency of one is between wTO,CdS and ωLO,CdS,and that of the other is between ωTO,HgS and ωLO,HgS.With the increasing of quantum number l,the frequency of each IO mode approaches one of the two frequency values of the single CdS/HgS heterostructure,and the potential for each IO mode is more and more localized at a certain at a certain interface,furthermore,the coupling between the electron-IO phonos becomes weaker.
