The response of a layered electron gas to a transverse electromagnetic field

Abstract

The propagation of transverse electromagnetic waves in a layered electron gas is studied from the point of view of the electromagnetic penetration depth. It is found that transverse in-plane plasmons can be observed in systems consisting of two layers of charge carriers per unit cell for special values of wave vector and frequency, determined by the intrinsic parameters of the set-up like the Fermi velocity and the length scales of the unit cell. The internal degrees of freedom in the two layers per unit cell as compared to one layer per unit cell make possible this acoustic-like transverse plasmon. Above the cut-off frequency transverse electromagnetic waves are attenuated as they propagate in the layered electron gas. The layered gas furthermore behaves like a three-dimensional free-electron gas when the layers are close, having the same penetration depth dependence on frequency and the electron relaxation time. In the opposite limit of remote layers the penetration depth is found to be almost independent of these parameters.