Electromagnetic Absorption in Two-dimensional Systems under a Magnetic Field and a Unidirectional Periodic Potential

Abstract

The absorption of electromagnetic waves by a high mobility two-dimensional electron gas subjected to a magnetic field and a weak periodic potential is investigated. We show that the periodic modulation on the Laudau states has a profound effect on the absorption of electromagnetic waves. We develop a formalism which treats the electron–electron interaction beyond the random-phase-approximation (RPA) and includes the electron-impurity scattering in the lowest order. A RPA dielectric function was employed to study the electromagnetic absorption in modulated systems. Simultaneous excitation of an electron–hole pair with finite momentum contributes significantly to the absorption around and below the cyclotron frequency. Such a process is absent for a uniform electron gas under a magnetic field.