Composite perovskite piezoelectric ceramics of PMMN quaternary system were prepared by cold-pressing and solid-phase sintering. Piezoelectric modulus and density of the samples were measured after polarization. X-ray ...Composite perovskite piezoelectric ceramics of PMMN quaternary system were prepared by cold-pressing and solid-phase sintering. Piezoelectric modulus and density of the samples were measured after polarization. X-ray diffraction analysis and SEM were used to prove the result that the major phase of the piezoelectric ceramic spectimen based on PZT is PZT phase,which is tetragonal system and P-4mm space group.展开更多
The piezoelectric ceramic transformer has been more and more widely applied in elec tronic devices of high voltage and small current due to its novel features in the high voltage field: very high voltage step-up ratio...The piezoelectric ceramic transformer has been more and more widely applied in elec tronic devices of high voltage and small current due to its novel features in the high voltage field: very high voltage step-up ratio, small in size, light in weight and non-metal material in use; it cannot be burnt while the load circuit is shorted, and broken down in high voltage field;展开更多
We investigate the collective plasma oscillations theoretically in multilayer 8-Pmmn borophene structures,where the tilted Dirac electrons in spatially separated layers are coupled via the Coulomb interaction.We calcu...We investigate the collective plasma oscillations theoretically in multilayer 8-Pmmn borophene structures,where the tilted Dirac electrons in spatially separated layers are coupled via the Coulomb interaction.We calculate the energy dispersions and Landau dampings of the multilayer plasmon excitations as a function of the total number of layers,the interlayer separation,and the different orientations.Like multilayer graphene,the plasmon spectrum in multilayer borophene consists of one in-phase optical mode and N-1 out-of-phase acoustical modes.We show that the plasmon modes possess kinks at the boundary of the interband single-particle continuum and the apparent anisotropic behavior.All the plasmon modes approach the same dispersion at a sufficiently large interlayer spacing in the short-wavelength limit.Especially along specific orientations,the optical mode could touch an energy maximum in the nondamping region,which shows non-monotonous behavior.Our work provides an understanding of the multilayer borophene plasmon and may pave the way for multilayer borophene-based plasmonic devices.展开更多
We investigate theoretically valley-resolved lateral shift of electrons traversing an n–p–n junction bulit on a typical tilted Dirac system(8-Pmmn borophene). A gauge-invariant formula on Goos–H?nchen(GH) shift of ...We investigate theoretically valley-resolved lateral shift of electrons traversing an n–p–n junction bulit on a typical tilted Dirac system(8-Pmmn borophene). A gauge-invariant formula on Goos–H?nchen(GH) shift of transmitted beams is derived, which holds for any anisotropic isoenergy surface. The tilt term brings valley dependence of relative position between the isoenergy surface in n region and that in the p region. Consequently, valley double refraction can occur at the n–p interface. The exiting positions of two valley-polarized beams depend on the incident angle and energy of incident beam and barrier parameters. Their spatial distance D can be enhanced to be ten to a hundred times larger than the barrier width. Due to tilting-induced high anisotropy of the isoenergy surface, D depends strongly on the barrier orientation. It is always zero when the junction is along the tilt direction of Dirac cones. Thus GH effect of transmitted beams in tilted Dirac systems can be utilized to design anisotropic and valleyresolved beam-splitter.展开更多
文摘Composite perovskite piezoelectric ceramics of PMMN quaternary system were prepared by cold-pressing and solid-phase sintering. Piezoelectric modulus and density of the samples were measured after polarization. X-ray diffraction analysis and SEM were used to prove the result that the major phase of the piezoelectric ceramic spectimen based on PZT is PZT phase,which is tetragonal system and P-4mm space group.
文摘The piezoelectric ceramic transformer has been more and more widely applied in elec tronic devices of high voltage and small current due to its novel features in the high voltage field: very high voltage step-up ratio, small in size, light in weight and non-metal material in use; it cannot be burnt while the load circuit is shorted, and broken down in high voltage field;
基金supported by the Scientific Research Program from Science and Technology Bureau of Chongqing City(Grant No.cstc2020jcyj-msxmX0684)the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202000639)in part by the National Natural Science Foundation of China(Grant No.12147102)。
文摘We investigate the collective plasma oscillations theoretically in multilayer 8-Pmmn borophene structures,where the tilted Dirac electrons in spatially separated layers are coupled via the Coulomb interaction.We calculate the energy dispersions and Landau dampings of the multilayer plasmon excitations as a function of the total number of layers,the interlayer separation,and the different orientations.Like multilayer graphene,the plasmon spectrum in multilayer borophene consists of one in-phase optical mode and N-1 out-of-phase acoustical modes.We show that the plasmon modes possess kinks at the boundary of the interband single-particle continuum and the apparent anisotropic behavior.All the plasmon modes approach the same dispersion at a sufficiently large interlayer spacing in the short-wavelength limit.Especially along specific orientations,the optical mode could touch an energy maximum in the nondamping region,which shows non-monotonous behavior.Our work provides an understanding of the multilayer borophene plasmon and may pave the way for multilayer borophene-based plasmonic devices.
基金supported by the National Natural Science Foundation of China(Grant No.11774314)。
文摘We investigate theoretically valley-resolved lateral shift of electrons traversing an n–p–n junction bulit on a typical tilted Dirac system(8-Pmmn borophene). A gauge-invariant formula on Goos–H?nchen(GH) shift of transmitted beams is derived, which holds for any anisotropic isoenergy surface. The tilt term brings valley dependence of relative position between the isoenergy surface in n region and that in the p region. Consequently, valley double refraction can occur at the n–p interface. The exiting positions of two valley-polarized beams depend on the incident angle and energy of incident beam and barrier parameters. Their spatial distance D can be enhanced to be ten to a hundred times larger than the barrier width. Due to tilting-induced high anisotropy of the isoenergy surface, D depends strongly on the barrier orientation. It is always zero when the junction is along the tilt direction of Dirac cones. Thus GH effect of transmitted beams in tilted Dirac systems can be utilized to design anisotropic and valleyresolved beam-splitter.
