We investigated Goos-Hänchen(GH)and Imbert-Fedorov(IF)shifts of a reflective beam on a twisted bilayer of hexagonal boron nitride(hBN),where a left circularly polarized beam was incident on the surface.Our result...We investigated Goos-Hänchen(GH)and Imbert-Fedorov(IF)shifts of a reflective beam on a twisted bilayer of hexagonal boron nitride(hBN),where a left circularly polarized beam was incident on the surface.Our results demonstrate that the twist angle between the two optical axes plays an important role in obtaining large shifts with a high reflectivity.The GH shift with 10λ_(0) is achieved,while the reflectivity is near 100%by tuning the twist angle.The maximum of the IF shift is found in the certain condition satisfied by the reflective coefficients,and the shift strongly depends on the twist angle between the optical axes of the two slabs.The spatial shifts obtained directly from the GH and IF shift definitions were provided,which indicate that the theoretical results from the stationary phase method are believable.These results may open up a new way for developing the nano-optical devices.展开更多
In the present work, vibrational and thermodynamic properties of XBi（X = B, Al, Ga, In） compounds are compared and investigated. The calculation is carried out using density functional theory（DFT） within the gener...In the present work, vibrational and thermodynamic properties of XBi（X = B, Al, Ga, In） compounds are compared and investigated. The calculation is carried out using density functional theory（DFT） within the generalized gradient approximation（GGA） in a plane wave basis, with ultrasoft pseudopotentials. The lattice dynamical properties are calculated using density functional perturbation theory（DFPT） as implemented in Quantum ESPRESSO（QE） code. Thermodynamic properties involving phonon density of states（DOS） and specific heat at constant volume are investigated using quasiharmonic approximation（QHA） package within QE. The phonon dispersion diagrams for InBi, GaBi, BBi, and AlBi indicate that there is no imaginary phonon frequency in the entire Brillouin zone, which proves the dynamical stability of these materials. BBi has the highest thermal conductivity and InBi has the lowest thermal conductivity. AlBi has the largest and GaBi has the smallest reststrahlen band which somehow suggests the polar property of XBi materials. The phonon gaps for InBi, GaBi, BBi and AlBi are about 160 cm^-1, 150 cm^-1, 300 cm^-1, and 150 cm^-1, respectively. For all compounds,the three acoustic modes near the gamma point have a linear behavior. C_V is a function of T-3 at low temperatures while for higher temperatures it asymptotically tends to a constant as expected.展开更多
基金supported by the Natural Science Foundation of Heilongjiang Province,China(Grant No.LH2020A014)Harbin Normal University Fund(Grant No.HSDSSCX202127)Education Commission of Heilongjiang Province,China(Grant No.2020-KYYWF352)。
文摘We investigated Goos-Hänchen(GH)and Imbert-Fedorov(IF)shifts of a reflective beam on a twisted bilayer of hexagonal boron nitride(hBN),where a left circularly polarized beam was incident on the surface.Our results demonstrate that the twist angle between the two optical axes plays an important role in obtaining large shifts with a high reflectivity.The GH shift with 10λ_(0) is achieved,while the reflectivity is near 100%by tuning the twist angle.The maximum of the IF shift is found in the certain condition satisfied by the reflective coefficients,and the shift strongly depends on the twist angle between the optical axes of the two slabs.The spatial shifts obtained directly from the GH and IF shift definitions were provided,which indicate that the theoretical results from the stationary phase method are believable.These results may open up a new way for developing the nano-optical devices.
文摘In the present work, vibrational and thermodynamic properties of XBi（X = B, Al, Ga, In） compounds are compared and investigated. The calculation is carried out using density functional theory（DFT） within the generalized gradient approximation（GGA） in a plane wave basis, with ultrasoft pseudopotentials. The lattice dynamical properties are calculated using density functional perturbation theory（DFPT） as implemented in Quantum ESPRESSO（QE） code. Thermodynamic properties involving phonon density of states（DOS） and specific heat at constant volume are investigated using quasiharmonic approximation（QHA） package within QE. The phonon dispersion diagrams for InBi, GaBi, BBi, and AlBi indicate that there is no imaginary phonon frequency in the entire Brillouin zone, which proves the dynamical stability of these materials. BBi has the highest thermal conductivity and InBi has the lowest thermal conductivity. AlBi has the largest and GaBi has the smallest reststrahlen band which somehow suggests the polar property of XBi materials. The phonon gaps for InBi, GaBi, BBi and AlBi are about 160 cm^-1, 150 cm^-1, 300 cm^-1, and 150 cm^-1, respectively. For all compounds,the three acoustic modes near the gamma point have a linear behavior. C_V is a function of T-3 at low temperatures while for higher temperatures it asymptotically tends to a constant as expected.
