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
The authors discuss the stability radius of the non-smooth Pritchard-Salamon systemsunder structured perturbations.A formula for the stability radius in terms of t he norm of a certaininput-output operator is obtained...The authors discuss the stability radius of the non-smooth Pritchard-Salamon systemsunder structured perturbations.A formula for the stability radius in terms of t he norm of a certaininput-output operator is obtained.Furthermore,the relationship between stability radius and thesolvability of some type of algebraic Riccati equations is given.展开更多
In this study, we used the crystal structure search method and first-principles calculations to systematically explore the highpressure phase diagrams of the TaAs family （NbP, NbAs, TaP, and TaAs）. Our calculation r...In this study, we used the crystal structure search method and first-principles calculations to systematically explore the highpressure phase diagrams of the TaAs family （NbP, NbAs, TaP, and TaAs）. Our calculation results show that NbAs and TaAs have similar phase diagrams, the same structural phase transition sequence I41md→Pδm2→}P21/c→Pm3m, and slightly different transition pressures. The phase transition sequence of NbP and TaP differs somewhat from that of NbAs and TaAs, in which new structures emerge, such as the Cmcm structure in NbP and the Pmmn structure in TaP. Interestingly, we found that in the electronic structure of the high-pressure phase Pδm2-NbAs, there are coexisting Weyl points and triple degenerate points, similar to those found in high-pressure Pδm2-TaAs.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.
基金supported by the National Natural Science Foundation of China under Grant Nos. 10626057 and 10571165
文摘The authors discuss the stability radius of the non-smooth Pritchard-Salamon systemsunder structured perturbations.A formula for the stability radius in terms of t he norm of a certaininput-output operator is obtained.Furthermore,the relationship between stability radius and thesolvability of some type of algebraic Riccati equations is given.
基金supported by the National Key R&D Program of China(Grant No.2016YFA0300404)the National Key Projects for Basic Research in China(Grant No.2015CB921202)+4 种基金the National Natural Science Foundation of China(Grant Nos.11574133,and 51372112)the Natural Science Foundation Jiangsu Province(Grant No.BK20150012)the Science Challenge Project(Grant No.TZ2016001)the Fundamental Research Funds for the Central UniversitiesSpecial Program for Applied Research on Super Computation of the National Natural Science FoundationGuangdong Joint Fund
文摘In this study, we used the crystal structure search method and first-principles calculations to systematically explore the highpressure phase diagrams of the TaAs family （NbP, NbAs, TaP, and TaAs）. Our calculation results show that NbAs and TaAs have similar phase diagrams, the same structural phase transition sequence I41md→Pδm2→}P21/c→Pm3m, and slightly different transition pressures. The phase transition sequence of NbP and TaP differs somewhat from that of NbAs and TaAs, in which new structures emerge, such as the Cmcm structure in NbP and the Pmmn structure in TaP. Interestingly, we found that in the electronic structure of the high-pressure phase Pδm2-NbAs, there are coexisting Weyl points and triple degenerate points, similar to those found in high-pressure Pδm2-TaAs.
