A combination of the iterative perturbation theory (ITP) of the dynamical mean field theory (DMFT) and coherentpotential approximation (CPA) is generalized to the double exchange model with orbital degeneracy. T...A combination of the iterative perturbation theory (ITP) of the dynamical mean field theory (DMFT) and coherentpotential approximation (CPA) is generalized to the double exchange model with orbital degeneracy. The Hubbard interaction and the off-diagonal components for the hopping matrix tij^mn(m ≠ n) are considered in our calculation of spectrum and optical conductivity. The numerical results show that the effects of the non-diagonal hopping matrix elements are important.展开更多
Based on the modification of the simplified coherent potential approximation(SCPA),a model is developed to calculate the composition dependence of the band gap energy of III-V ternary alloys with the same anion.The de...Based on the modification of the simplified coherent potential approximation(SCPA),a model is developed to calculate the composition dependence of the band gap energy of III-V ternary alloys with the same anion.The derived equation is used to fit the experimental band gap energy of In x Al 1 x N,In x Ga 1 x N and Al x Ga 1 x N with x from 0 to 1.It is found that the fitting results are better than those done by using SCPA.The fitting results are also better than those obtained by using the formula with a small bowing coefficient,especially for In x Al 1 x N.In addition,our model can also be used to describe the composition dependence of band gap energy of other III-V ternary alloys.展开更多
The coherent potential approximation (CPA) was used in the calculation of the vibrational spectra for absorbed 12CO/13CO thextures on platinum. The theoretical results were compared with the surface IR-spectra of 12CO...The coherent potential approximation (CPA) was used in the calculation of the vibrational spectra for absorbed 12CO/13CO thextures on platinum. The theoretical results were compared with the surface IR-spectra of 12CO/13CO mixture absorbed on Pt-electrode. The results show that in the systems consisting of isotopic Anxtures of CO on Pt(001), molecules interact mainly through their dipole fields.展开更多
Using the two-dimensional ionic Hubbard model as a simple basis for describing the electronic structure of silicene in the presence of an electric field induced by the substrate, we use the coherent-potential approxim...Using the two-dimensional ionic Hubbard model as a simple basis for describing the electronic structure of silicene in the presence of an electric field induced by the substrate, we use the coherent-potential approximation to calculate tbe zero-temperature phase diagram and the associated spectral function at half filling. We find that any degree of symmetry- breaking induced by the electric field causes the silicene structure to lose its Dirac fermion characteristics, thus providing a simple mechanism for the disappearance of the Dirac cone.展开更多
Using the rigorous multiple-scattering theory, we study the dispersion relation of electromagnetic (EM) waves in two dimensional dielectric photonic crystals (PCs) and metallic photonic crystals (MPCs) in the lo...Using the rigorous multiple-scattering theory, we study the dispersion relation of electromagnetic (EM) waves in two dimensional dielectric photonic crystals (PCs) and metallic photonic crystals (MPCs) in the low-frequency limit. Analytic formula for the effective velocity of EM waves in PCs and MPCs is obtained. Accuracy of our formula is checked by comparing the results with rigorous calculations. For PCs, our result is exactly the same as the coherent potential approximation (CPA), which is accurate even when the filling fraction is high. But for MPCs, our approach demonstrates special advantages, while the CPA theory fails, in predicting the effective velocity of EM waves in MPCs at low frequency.展开更多
The triatomic and tetratomic gas molecule adsorption effects on the electrical conductivity of graphene areinvestigated by the tight-binding model,Green’s function method,and coherent potential approximation.We find ...The triatomic and tetratomic gas molecule adsorption effects on the electrical conductivity of graphene areinvestigated by the tight-binding model,Green’s function method,and coherent potential approximation.We find thatthe electrical conductivity of graphene sheet is sensitive to the adsorption of these gases.展开更多
The coherent potential approximation(CPA)within full counting statistics(FCS)formalism is shown to be a suitable method to investigate average electric conductance,shot noise as well as higher order cumulants in disor...The coherent potential approximation(CPA)within full counting statistics(FCS)formalism is shown to be a suitable method to investigate average electric conductance,shot noise as well as higher order cumulants in disordered systems.We develop a similar FCS-CPA formalism for phonon transport through disordered systems.As a byproduct,we derive relations among coefficients of different phonon current cumulants.We apply the FCS-CPA method to investigate phonon transport properties of graphene systems in the presence of disorders.For binary disorders as well as Anderson disorders,we calculate up to the 8-th phonon transmission moments and demonstrate that the numerical results of the FCS-CPA method agree very well with that of the brute force method.The benchmark shows that the FCS-CPA method achieves 20 times more speedup ratio.Collective features of phonon current cumulants are also revealed.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No 60476047)the Natural Science Foundation of Henan Province, China (Grant No 0411011700)
文摘A combination of the iterative perturbation theory (ITP) of the dynamical mean field theory (DMFT) and coherentpotential approximation (CPA) is generalized to the double exchange model with orbital degeneracy. The Hubbard interaction and the off-diagonal components for the hopping matrix tij^mn(m ≠ n) are considered in our calculation of spectrum and optical conductivity. The numerical results show that the effects of the non-diagonal hopping matrix elements are important.
基金supported by the Special Funds for Major State Basic Research Project (Grant No. 2011CB301900)the National Natural Science Foundation of China (Grant No. 60990311)
文摘Based on the modification of the simplified coherent potential approximation(SCPA),a model is developed to calculate the composition dependence of the band gap energy of III-V ternary alloys with the same anion.The derived equation is used to fit the experimental band gap energy of In x Al 1 x N,In x Ga 1 x N and Al x Ga 1 x N with x from 0 to 1.It is found that the fitting results are better than those done by using SCPA.The fitting results are also better than those obtained by using the formula with a small bowing coefficient,especially for In x Al 1 x N.In addition,our model can also be used to describe the composition dependence of band gap energy of other III-V ternary alloys.
文摘The coherent potential approximation (CPA) was used in the calculation of the vibrational spectra for absorbed 12CO/13CO thextures on platinum. The theoretical results were compared with the surface IR-spectra of 12CO/13CO mixture absorbed on Pt-electrode. The results show that in the systems consisting of isotopic Anxtures of CO on Pt(001), molecules interact mainly through their dipole fields.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11174219)the Program for New Century Excellent Talents in Universities,China (Grant No. NCET-13-0428)+2 种基金the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20110072110044)the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, Chinathe Scientific Research Foundation for the Returned Overseas Chinese Scholars of the Education Ministry of China
文摘Using the two-dimensional ionic Hubbard model as a simple basis for describing the electronic structure of silicene in the presence of an electric field induced by the substrate, we use the coherent-potential approximation to calculate tbe zero-temperature phase diagram and the associated spectral function at half filling. We find that any degree of symmetry- breaking induced by the electric field causes the silicene structure to lose its Dirac fermion characteristics, thus providing a simple mechanism for the disappearance of the Dirac cone.
基金Supported by the National Natural Science Foundation of China (50425206, 50702038)
文摘Using the rigorous multiple-scattering theory, we study the dispersion relation of electromagnetic (EM) waves in two dimensional dielectric photonic crystals (PCs) and metallic photonic crystals (MPCs) in the low-frequency limit. Analytic formula for the effective velocity of EM waves in PCs and MPCs is obtained. Accuracy of our formula is checked by comparing the results with rigorous calculations. For PCs, our result is exactly the same as the coherent potential approximation (CPA), which is accurate even when the filling fraction is high. But for MPCs, our approach demonstrates special advantages, while the CPA theory fails, in predicting the effective velocity of EM waves in MPCs at low frequency.
文摘The triatomic and tetratomic gas molecule adsorption effects on the electrical conductivity of graphene areinvestigated by the tight-binding model,Green’s function method,and coherent potential approximation.We find thatthe electrical conductivity of graphene sheet is sensitive to the adsorption of these gases.
基金the National Natural Science Foundation of China(Grant No.12034014)the Natural Science Foundation of Guangdong Province(Grant No.2020A1515011418).
文摘The coherent potential approximation(CPA)within full counting statistics(FCS)formalism is shown to be a suitable method to investigate average electric conductance,shot noise as well as higher order cumulants in disordered systems.We develop a similar FCS-CPA formalism for phonon transport through disordered systems.As a byproduct,we derive relations among coefficients of different phonon current cumulants.We apply the FCS-CPA method to investigate phonon transport properties of graphene systems in the presence of disorders.For binary disorders as well as Anderson disorders,we calculate up to the 8-th phonon transmission moments and demonstrate that the numerical results of the FCS-CPA method agree very well with that of the brute force method.The benchmark shows that the FCS-CPA method achieves 20 times more speedup ratio.Collective features of phonon current cumulants are also revealed.