By using the Kubo formula, the optical conductivity of strained black phosphorene was studied. The anisotropic band dispersion gives rise to an orientation dependent optical conductivity. The energy gap can be tuned by the uniaxial and biaxial strains which can be observed from the interband optical conductivity polarized along the armchair (x) direction. The preferential conducting direction is along the x direction. The dependence of the intraband optical conductivity along the zigzag (y) direction on the Fermi energy and strain exhibits increasing or decreasing monotonously. However, along the x direction this dependence is complicated which originates from the carriers' inverse-direction movements obtained by two types of the nearest phosphorus atom interactions. The modification of the biaxial strain on the energy structure and optical-absorption property is more effective. The imaginary part of the total optical conductivity (Imσ ) can be negative around the threshold of the interband optical transition by modifying the chemical potential. Away from this frequency region, Imσ exhibits positive value. It can be used in the application of the surface plasmon propagations in multilayer dielectric structures. PHYSICAL REVIEW B 97, 245408 (2018) † k,s ψ * (r) where c † k,s and c k,s are the creation and annihilation operators for an electron at (k,s) state. In the second quantized notation, the Hamiltonian can be written as H = k,s E k,s c † k,s c k,s + J · A. The components J μ=x,y of the current operator J are
The electronic structure, lattice dynamics, and electron–phonon coupling (EPC) of electron (n)-doped LiH have been extensively studied using ab initio methods within the virtual crystal approximation. The overall agreement of the lattice constants and bulk modulus for pure LiH with the experiments is excellent if the zero-point motion is taken into account. From the theoretical calculation for n-doped LiH, it is indicated that metallic n-doped LiH might be a good superconductor. Moreover, the EPC parameter λ for n-doped LiH was found to increase with the dopant concentration, resulting from the softening of optical phonon modes and the increase of the electron density of states at the Fermi level, while a decreasing trend of λ was predicted for the presence of pressure. Phonon linewidth calculations suggested that the optical phonon mode makes the main contribution to the EPC. A possible mechanism for the predicted superconductivity of n-doped LiH has been discussed.
The ZnO nanocombs were synthesized by chemical vapor deposition method, which the uniform and dense nanotips were along one side of the comb ribbon. The growth mechanism was described as free catalyst self-assembled and vapor-solid model. The optical properties related with the surface states were investigated by Raman and PL spectra. The large redshift of 1LO phonon peak was attributed to the surface and interface states. The normalized PL spectra showed that the deep-level emission decreased for the sample to be annealed in O2 ambient at 500 degrees C. On the contrary, the deep-level emission increased while for the annealed sample in O2 ambient at 600 degrees C. The deep-level emission was attributed to the transition from the shallow donor to the deep acceptor. The XPS analysis showed the existence of oxygen rich and Zn deficient in the ZnO nanocombs annealed at 600 degrees C. The abnormal temperature dependence of integrated PL intensity was attributed to the abundant surface states.
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