Far-infrared surface-Landau-level spectroscopy in Bi

Abstract

Surface-Landau-level resonance data in Bi are presented at four far-infrared frequencies: 890.7, 1362.5, 1747.1, and 2526.6 GHz. The magnetic field positions of the resonances compare well with the predictions of a semiclassical calculation which takes into account the deviation from the well-established theory for the surface-state resonances valid at microwave frequencies. These deviations occur in the far-infrared primarily because the excitation energy $\hslash \omega$ becomes comparable to the Bi Fermi energy. We incorporate nonparabolic effects into the semiclassical calculation by using the two-band model to describe surface Landau levels in the nonparabolic conduction band of Bi. The influence of the far-infrared effects on line shape is discussed together with the lack of observable surface-roughness scattering.