The problem of bound polarons in quantum dot quantum well （QDQW） structures is studied theoretically. The eigenfrequencies of bulk longitudinal optical （LO） and surface optical （SO） modes are derived in the fram...The problem of bound polarons in quantum dot quantum well （QDQW） structures is studied theoretically. The eigenfrequencies of bulk longitudinal optical （LO） and surface optical （SO） modes are derived in the framework of the dielectric continuum approximation. The electron-phonon interaction Hamiltonian for QDQW structures is obtained and the exchange interaction between impurity and LO-phonons is discussed. The binding energy and the trapping energy of the bound polaron in CdS/HgS QDQW structures are calculated. The numerical results reveal that there exist three branches of eigenfrequencies of surface optical vibration in the CdS/HgS QDQW structure. It is also shown that the binding energy and the trapping energy increase as the inner radius of the QDQW structure decreases, with the outer radius fixed, and the trapping energy takes a major part of the binding energy when the inner radius is very small.展开更多
With hydrogen-like impurity（HLI） located in the center of Cs I quantum pseudodot（QPD） and by using the variational method of Pekar type（VMPT）, we investigate the first-excited state energy（FESE）, excitation en...With hydrogen-like impurity（HLI） located in the center of Cs I quantum pseudodot（QPD） and by using the variational method of Pekar type（VMPT）, we investigate the first-excited state energy（FESE）, excitation energy and transition frequency of the strongly-coupled bound polaron in the present paper. Temperature effects on bound polaron properties are calculated by employing the quantum statistical theory（QST）. According to the present work＇s numerical results, the FESE, excitation energy and transition frequency decay（amplify） with raising temperature in the regime of lower（higher）temperature. They are decreasing functions of Coulomb impurity potential strength.展开更多
Feynman variational path-integral theory was used to obtain the groud-state energy of a polaron in a quantum well in the presence of a Coulomb potential for arbitray values of the electron-phonon couplng constant α.N...Feynman variational path-integral theory was used to obtain the groud-state energy of a polaron in a quantum well in the presence of a Coulomb potential for arbitray values of the electron-phonon couplng constant α.Numerical and analytical results showed that the energy shift was more sensitive to α than to the Coulomb binding parameter(β) and increased with the decrease of effective quantum well width lZ.it was intersting that due to the electronic confinement in the quasi-2D(quantum well)structures,the lower bound of the strong coupling regime was shifted to smaller values of α.Comparison of the polaron in the quantum well with that in the quantum wire or dot showed that the polaronic effect strengthened with decrease of the confinement dimension.展开更多
By a combination method of Lee-Low-Pines unitary transformation method and Pekar-type variational method,the ground state energy(GSE)of the bound polaron is studied in the asymmetrical Gaussian potential quantum well ...By a combination method of Lee-Low-Pines unitary transformation method and Pekar-type variational method,the ground state energy(GSE)of the bound polaron is studied in the asymmetrical Gaussian potential quantum well considering the temperature and electromagneticfield.The impacts of the temperature and asymmetrical Gaussian potential,electromagnetic field and phonon-electron coupling upon the GSE are obtained.The results show that the GSE of the bound polaron not only oscillates as the temperature changes regardless of the electromagneticfield and asymmetrical Gaussian potential and Coulomb impurity potential(CIP)and electron-phonon coupling but also has different rules with the electromagnetic field and asymmetrical Gaussian potential and CIP and electron-phonon coupling at different temperature zones.展开更多
Within the effective-mass approximation,a variational method is adopted to investigate the polaron effect in a strained GaN/Al_xGa_（1-x）N cylindrical quantum dot.The electron couples with both branches of longitudin...Within the effective-mass approximation,a variational method is adopted to investigate the polaron effect in a strained GaN/Al_xGa_（1-x）N cylindrical quantum dot.The electron couples with both branches of longitudinal optical-like（LO-like）and transverse optical-like（TO-like）phonons and the built-in electric field are taken into account.The numerical results show that the binding energy of the bound polaron is reduced obviously by the polaron effect on the impurity states.Furthermore,the contribution of LO-like phonons to the binding energy is dominant,and the anisotropic angle and Al content influence on the binding energy are small.展开更多
The binding energies of bound polarons near the interface of a strained wurtzite GaN/Al_xGa_（1-x）N het-erojunction are studied by using a modified LLP variational method and a simplified coherent potential approxima...The binding energies of bound polarons near the interface of a strained wurtzite GaN/Al_xGa_（1-x）N het-erojunction are studied by using a modified LLP variational method and a simplified coherent potential approximation under hydrostatic pressure and an external electric field.Considering the biaxial strain due to lattice mismatch or epitaxial growth,the uniaxial strain effects and the influences of the electron-phonon interaction as well as impurity-phonon interaction including the effects of interface-optical phonon modes and half-space phonon modes,the binding energies as functions of pressure,the impurity position,areal electron density and the phonon effect on the Stark energy shift are investigated.The numerical result shows that the contributions from the interface optical phonon mode with higher frequency and the LO-like half space mode to the binding energy and the Stark energy shift are important and obviously increase with increasing hydrostatic pressure,whereas the interface optical phonon mode with lower frequency and the TO-like half space mode are extremely small and are insensitive to the impurity position and hydrostatic pressure.It is also shown that the conductive band bending should not be neglected.展开更多
基金supported by Universities Program of Inner Mongol of China(Grant No NJZZ07008)the Natural Science Foundation of Inner Mongol of China(Grant No 200607010105)
文摘The problem of bound polarons in quantum dot quantum well （QDQW） structures is studied theoretically. The eigenfrequencies of bulk longitudinal optical （LO） and surface optical （SO） modes are derived in the framework of the dielectric continuum approximation. The electron-phonon interaction Hamiltonian for QDQW structures is obtained and the exchange interaction between impurity and LO-phonons is discussed. The binding energy and the trapping energy of the bound polaron in CdS/HgS QDQW structures are calculated. The numerical results reveal that there exist three branches of eigenfrequencies of surface optical vibration in the CdS/HgS QDQW structure. It is also shown that the binding energy and the trapping energy increase as the inner radius of the QDQW structure decreases, with the outer radius fixed, and the trapping energy takes a major part of the binding energy when the inner radius is very small.
基金Project supported by the National Natural Science Foundation of China(Grant No.11464033)
文摘With hydrogen-like impurity（HLI） located in the center of Cs I quantum pseudodot（QPD） and by using the variational method of Pekar type（VMPT）, we investigate the first-excited state energy（FESE）, excitation energy and transition frequency of the strongly-coupled bound polaron in the present paper. Temperature effects on bound polaron properties are calculated by employing the quantum statistical theory（QST）. According to the present work＇s numerical results, the FESE, excitation energy and transition frequency decay（amplify） with raising temperature in the regime of lower（higher）temperature. They are decreasing functions of Coulomb impurity potential strength.
文摘Feynman variational path-integral theory was used to obtain the groud-state energy of a polaron in a quantum well in the presence of a Coulomb potential for arbitray values of the electron-phonon couplng constant α.Numerical and analytical results showed that the energy shift was more sensitive to α than to the Coulomb binding parameter(β) and increased with the decrease of effective quantum well width lZ.it was intersting that due to the electronic confinement in the quasi-2D(quantum well)structures,the lower bound of the strong coupling regime was shifted to smaller values of α.Comparison of the polaron in the quantum well with that in the quantum wire or dot showed that the polaronic effect strengthened with decrease of the confinement dimension.
基金supported by the National Natural Science Foundation of China under Grant No.11975011。
文摘By a combination method of Lee-Low-Pines unitary transformation method and Pekar-type variational method,the ground state energy(GSE)of the bound polaron is studied in the asymmetrical Gaussian potential quantum well considering the temperature and electromagneticfield.The impacts of the temperature and asymmetrical Gaussian potential,electromagnetic field and phonon-electron coupling upon the GSE are obtained.The results show that the GSE of the bound polaron not only oscillates as the temperature changes regardless of the electromagneticfield and asymmetrical Gaussian potential and Coulomb impurity potential(CIP)and electron-phonon coupling but also has different rules with the electromagnetic field and asymmetrical Gaussian potential and CIP and electron-phonon coupling at different temperature zones.
基金supported by the National Natural Science Foundation of China(No10964006)the Research Funds for the Science and Technology Innovation Team of Inner Mongolia Agricultural University(NoNDPYTD2010-7)
文摘Within the effective-mass approximation,a variational method is adopted to investigate the polaron effect in a strained GaN/Al_xGa_（1-x）N cylindrical quantum dot.The electron couples with both branches of longitudinal optical-like（LO-like）and transverse optical-like（TO-like）phonons and the built-in electric field are taken into account.The numerical results show that the binding energy of the bound polaron is reduced obviously by the polaron effect on the impurity states.Furthermore,the contribution of LO-like phonons to the binding energy is dominant,and the anisotropic angle and Al content influence on the binding energy are small.
基金supported by the National Natural Science Foundation of China(No.60966001)the Key Project of Natural Science Foundation of Inner Mongolia Autonomous Region,China(No.20080404Zd02)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20070126001).
文摘The binding energies of bound polarons near the interface of a strained wurtzite GaN/Al_xGa_（1-x）N het-erojunction are studied by using a modified LLP variational method and a simplified coherent potential approximation under hydrostatic pressure and an external electric field.Considering the biaxial strain due to lattice mismatch or epitaxial growth,the uniaxial strain effects and the influences of the electron-phonon interaction as well as impurity-phonon interaction including the effects of interface-optical phonon modes and half-space phonon modes,the binding energies as functions of pressure,the impurity position,areal electron density and the phonon effect on the Stark energy shift are investigated.The numerical result shows that the contributions from the interface optical phonon mode with higher frequency and the LO-like half space mode to the binding energy and the Stark energy shift are important and obviously increase with increasing hydrostatic pressure,whereas the interface optical phonon mode with lower frequency and the TO-like half space mode are extremely small and are insensitive to the impurity position and hydrostatic pressure.It is also shown that the conductive band bending should not be neglected.
