Selection rule for Raman spectra of two-dimensional materials using circularly-polarized vortex light.

Conservation of spin and orbital angular momenta of circularly-polarized vortex light is discussed for Raman spectra of two-dimensional materials. We first show the selection rule for optical absorption of two-dimensional materials as a function of the spin and orbital angular momentum of incident vortex light. In the case of two-dimensional materials, the Raman tensor for the incident vortex light does not change the symmetry of the phonon mode.

Effective impedance of two-dimensional metal with retardation effect.

Optical absorption with retardation effect is discussed for two-dimensional (2D) metal. The absorption is given by the induced Joule heat in the metal and it is proportional to Re()/||in whichanddenote conductivity and dielectric function, respectively. Here, we investigate the effective impedance in both retarded and non-retarded regions of surface plasmon by discussing the response of the current density to the electric fields.

Step-like conductance of a silicene pseudospin junction.

A step-like conductance as a function of the Fermi energy is theoretically predicted for a junction made of silicene, in which the energy gap in the junction can be controlled by a perpendicular electric field. When the electric field is applied at the central area of the junction, the transmission probability of an electron becomes partially suppressed and the calculated conductance behaves a step-like function of the Fermi energy. Origins of the step-like conductance are (1) formation of a standing-wave of electron, (2) changing number of transport channels and (3) a rotation of out-of-plane pseudospin of the electron in silicene.

Non-vertical optical transition in near-field enhanced spectroscopy of graphene.

We theoretically investigate the optical transition of an electron in graphene that is excited by near-field around a conical Au tip. The interaction between the near-field and the electron is calculated by tight-binding method. In the case of near-field, the wavevector of the electron changes by the optical absorption from the valence band to the conduction band.