Ballistic Hot Electron Transport in Graphene

We theoretically study the inelastic scattering rate and the carrier mean free path for energetic hot electrons in graphene, including both electron-electron and electron-phonon interactions. Taking account of optical phonon emission and electron-electron scattering, we find that the inelastic scattering time $\tau \sim 10^{-2}-10^{-1} \mathrm{ps}$ and the mean free path $l \sim 10-10^2 \mathrm{nm}$ for electron densities $n = 10^{12}-10^{13} \mathrm{cm}^{-2}$. In particular, we find that the mean free path exhibits a finite jump at the phonon energy $200 \mathrm{meV}$ due to electron-phonon interaction. Our results are directly applicable to device structures where ballistic transport is relevant with inelastic scattering dominating over elastic scattering.Comment: 4 page

Quantized Casimir Force

We investigate the Casimir effect between two-dimensional electron systems driven to the quantum Hall regime by a strong perpendicular magnetic field. In the large separation (d) limit where retardation effects are essential we find i) that the Casimir force is quantized in units of 3\hbar c \alpha^2/(8\pi^2 d^4), and ii) that the force is repulsive for mirrors with same type of carrier, and attractive for mirrors with opposite types of carrier. The sign of the Casimir force is therefore electrically tunable in ambipolar materials like graphene. The Casimir force is suppressed when one mirror is a charge-neutral graphene system in a filling factor \nu=0 quantum Hall state.Comment: 4.2 page

Differential-geometry scaling method for electromagnetic field and its applications to coaxial waveguide junctions

It is well-known that in mechanics and fluid dynamics one can transform or scale one problem and its solution to create a whole class of equivalent problems and their solutions[1]. Different problems and their solution behaviors of one equivalent class may look very different, but among them there are properties they share. The essence of such a scaling is to get appropriate dimensionless parameters that are common to them all