The influence of the electron-phonon coupling on the energy of low-lying states of the barrier D<SUP>-</SUP> center, which consists of a positive ion located on the z-axis at a distance from the two-dimens...The influence of the electron-phonon coupling on the energy of low-lying states of the barrier D<SUP>-</SUP> center, which consists of a positive ion located on the z-axis at a distance from the two-dimensional quantum dot plane and two electrons in the dot plane bound by the ion, is investigated at arbitrary strength of magnetic field by making use of the method of few-body physics. Discontinuous ground-state energy transitions induced by the magnetic field are reported. The dependence of the binding energy of the D<SUP>-</SUP> ground state on the quantum dot radius is obtained. A considerable enhancement of the binding is found for the D<SUP>-</SUP> ground state, which results from the confinement of electrons and electron-phonon coupling.展开更多
We adopt the nonequilibrium Green＇s function method to theoretically study the Kondo effect in a deformed molecule, which is treated as an electron-phonon interaction （EPI） system. The self-energy for phonon part i...We adopt the nonequilibrium Green＇s function method to theoretically study the Kondo effect in a deformed molecule, which is treated as an electron-phonon interaction （EPI） system. The self-energy for phonon part is calculated in the standard many-body diagrammatic expansion up to the second order in EPI strength. We find that the multiple phonon-assisted Kondo satellites arise besides the usual Kondo resonance. In the antiparallel magnetic configuration the splitting of main Kondo peak and phonon-assisted satellites only happen for asymmetrical dot-lead couplings, but it is free from the symmetry for the parallel magnetic configuration. The EPI strength and vibrational frequency can enhance the spin splitting of both main Kondo and satellites. It is shown that the suppressed zero-bias Kondo resonance can be restored by applying an external magnetic field, whose magnitude is dependent on the phononic effect remarkably. Although the asymmetry in tunnel coupling has no contribution to the restoration of spin splitting of Kondo peak, it can shrink the external field needed to switch tunneling magnetoresistance ratio between large negative dip and large positive peak.展开更多
Using an equation-of-motion technique, we theoretically study the Kondo-Fano effect in the T-shaped double quantum dots coupled to two ferromagnetic leads by the Anderson Hamiltonian. We calculate the density of state...Using an equation-of-motion technique, we theoretically study the Kondo-Fano effect in the T-shaped double quantum dots coupled to two ferromagnetic leads by the Anderson Hamiltonian. We calculate the density of states in this system by solving Green function. Our results reveal that the density of states show some noticeable characteristics not only depending upon the interdot coupling tab, the energy level eal of the side coupled quantum dot QDb, and the relative angle θ of magnetic moment M, but also the asymmetry parameter a in ferromagnetic leads and so on. All these parameters greatly influence the density of states of the eentral quantum dot QDa. This system is a possible candidate for spin valve transistors and may have potential applications in the spintronies.展开更多
We theoretically investigate the spin splitting in four undoped asymmetric quantum wells in the absence of external electric field and magnetic field.The quantum well geometry dependence of spin splitting is studied w...We theoretically investigate the spin splitting in four undoped asymmetric quantum wells in the absence of external electric field and magnetic field.The quantum well geometry dependence of spin splitting is studied with the Rashba and the Dresselhaus spin-orbit coupling included.The results show that the structure of quantum well plays an important role in spin splitting.The Rashba and the Dresselhaus spin splitting in four asymmetric quantum wells are quite different.The origin of the distinction is discussed in this work.展开更多
文摘The influence of the electron-phonon coupling on the energy of low-lying states of the barrier D<SUP>-</SUP> center, which consists of a positive ion located on the z-axis at a distance from the two-dimensional quantum dot plane and two electrons in the dot plane bound by the ion, is investigated at arbitrary strength of magnetic field by making use of the method of few-body physics. Discontinuous ground-state energy transitions induced by the magnetic field are reported. The dependence of the binding energy of the D<SUP>-</SUP> ground state on the quantum dot radius is obtained. A considerable enhancement of the binding is found for the D<SUP>-</SUP> ground state, which results from the confinement of electrons and electron-phonon coupling.
基金Supported by the National Natural Science Foundation of China under Grant No. 10974058the Guangdong Natural Science Foundation under Grant No. 9451063101002088+1 种基金the Shanghai Natural Science Foundation of China under Grant No. 09ZR1421400Science and Technology Program of Shanghai Maritime University under Contract No. 2008475
文摘We adopt the nonequilibrium Green＇s function method to theoretically study the Kondo effect in a deformed molecule, which is treated as an electron-phonon interaction （EPI） system. The self-energy for phonon part is calculated in the standard many-body diagrammatic expansion up to the second order in EPI strength. We find that the multiple phonon-assisted Kondo satellites arise besides the usual Kondo resonance. In the antiparallel magnetic configuration the splitting of main Kondo peak and phonon-assisted satellites only happen for asymmetrical dot-lead couplings, but it is free from the symmetry for the parallel magnetic configuration. The EPI strength and vibrational frequency can enhance the spin splitting of both main Kondo and satellites. It is shown that the suppressed zero-bias Kondo resonance can be restored by applying an external magnetic field, whose magnitude is dependent on the phononic effect remarkably. Although the asymmetry in tunnel coupling has no contribution to the restoration of spin splitting of Kondo peak, it can shrink the external field needed to switch tunneling magnetoresistance ratio between large negative dip and large positive peak.
基金Supported by the Scientific Research Fund of Southwest Petroleum University
文摘Using an equation-of-motion technique, we theoretically study the Kondo-Fano effect in the T-shaped double quantum dots coupled to two ferromagnetic leads by the Anderson Hamiltonian. We calculate the density of states in this system by solving Green function. Our results reveal that the density of states show some noticeable characteristics not only depending upon the interdot coupling tab, the energy level eal of the side coupled quantum dot QDb, and the relative angle θ of magnetic moment M, but also the asymmetry parameter a in ferromagnetic leads and so on. All these parameters greatly influence the density of states of the eentral quantum dot QDa. This system is a possible candidate for spin valve transistors and may have potential applications in the spintronies.
基金Supported by Scientific Research Fund of Zhejiang Provincial Education Department,China under Grant No. Y201120799Key Laboratory of Semiconductor Materials Science,Institute of Semiconductors,Chinese Academy of Science
文摘We theoretically investigate the spin splitting in four undoped asymmetric quantum wells in the absence of external electric field and magnetic field.The quantum well geometry dependence of spin splitting is studied with the Rashba and the Dresselhaus spin-orbit coupling included.The results show that the structure of quantum well plays an important role in spin splitting.The Rashba and the Dresselhaus spin splitting in four asymmetric quantum wells are quite different.The origin of the distinction is discussed in this work.
