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Nguyen Quang Bau,Dao Thu Hang,Do Tuan Long 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.12
The quantum magneto-thermoelectric effect in a two-dimensional compositional superlattice under the influence of an electromagnetic wave (EMW) in two cases is investigated. Two cases of the electron scattering mechanism are considered: the electron-acoustic phonon scattering and electron-optical phonon scattering. Analytical expressions for the quantum Ettingshausen coefficient (EC), the thermopower tensor, the thermoelectric tensor and the kinetic tensor are obtained by using a quantum kinetic equation. These expressions are numerically solved for the two-dimensional compositional superlattice GaAs/AlGaAs and the results are discussed. The results show that in the case of electron-acoustic phonon scattering, the Shubnikov-de Haas oscillations appear when we examine the dependences of the quantum EC, the thermopower tensor and the thermoelectric tensor on the magnetic field. In the case of electron-optical phonon scattering, resonance peaks that satisfy the condition of the inter-subband magneto-phonon resonance appear. In the two cases, the superlattice period (a parameter specific to the material) strongly affects the quantum magneto-thermoelectric effect. When the superlattice period is small, quantum EC oscillations (in the case of electron-acoustic phonon interaction) and quantum EC resonance peaks (in the case of electron-optical phonon interaction) appear. However, when the superlattice period is large, these oscillations and resonance peaks are not observed. Especially, the influence of electromagnetic waves on the quantum magneto-thermoelectric effect is also clarified. The quantum theory of the magneto-thermoelectric effect has been studied from low temperature to high temperature. This overcomes the limitations of the Boltzmann kinetic equation which was studied at high temperature. The results are new and can serve as a basis for further development of the theory of quantum magneto-thermoelectric effects in low-dimensional semiconductor systems.
Bau Nguyen Quang,Quynh Nguyen Thi Lam,Ba Cao Thi Vi,Hung Le Thai 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.12
Photo-stimulated quantum thermo-magnetoelectric effects in doped two-dimensional semiconductor superlattices, including the photo-stimulated quantum Ettingshausen effect and the photo-stimulated quantum Peltier effect, have been theoretically studied by using the quantum kinetic equation method. In this work, we assume that the electron-confined acoustic phonon scattering is essential. Moreover, the presence of the laser radiation (LR) is also taken into account to determine the influence of confined phonons on the aforementioned effects. We have defined the analytical expressions for the kinetic tensors and the Ettingshausen and the Peltier coefficients, presented the numerically calculated the theoretical results for the GaAs:Si/GaAs:Be doped semiconductor superlattice and compared them with these for the case of an unconfined acoustic phonon. The results obtained indicated that the formulas for the kinetic tensors, the Ettingshausen coefficient (EC) and the Peltier coefficient (PC) contain the quantum number m specifying the confinement of a phonon and approach the results for an unconfined phonon as m goes to zero. We found that the kinetic tensors, the EC and the PC oscillate with changing magnetic field and that the confinement of a phonon causes a shift of the peaks in these oscillations to lower energy. The dependences of both EC and PC on the temperature were found to be nonlinear. Moreover, all the coefficients level off when the temperature was less than 4.5 K or greater than 5.5 K. The EC also depended on the doping concentration in a nonlinear way and reaches a positive constant value when the semiconductor superlattice was doped with a high concentration. Most of the numerical results showed that the magnitude of the tensors, the EC as well as the PC, within a confined acoustic phonon varie significantly in comparison with the unconfined phonon case. This means that the confinement of the phonon affects the thermo-magnetoelectric effect quantitatively and qualitatively. These results contribute to completing the theory of the thermo-magnetoelectric effects in the low-dimensional semiconductor systems.