Cyclotron resonance and spin states in GaAs/Ga1−xAl

Abstract

The cyclotron resonance of high-mobility GaAs/Al x Ga 1Ϫx As heterojunctions displays both a temperature and Landau-level occupancy dependence. For occupancies below ϳ1/10, the behavior is identical to that found in high-purity bulk GaAs with spin splitting of the resonance. The position of the two peaks changes only slightly as the temperature is raised from 0.1 to 2 K. For 1 10 рр 1 6 , the peak position and relative peak intensity of the two peaks shifts radically as the temperature is raised or the density varied. At integral and greater occupancies only a single cyclotron resonance peak is observed whose position changes very little with temperature. Finally, the fractional regime with occupancies between 1 6 and 1 shows only a single cyclotron resonance with a slight temperature dependence and provides no evidence that the many-body interactions responsible for the fractional quantum Hall effect influence the cyclotron resonance. The experimental cyclotron resonance behavior can be explained by a recently published theory by Cooper and Chalker which models the system in terms of the Coulomb interaction and the thermal population of both spin states. A rigorous comparison between data taken over a wide range of densities and temperatures and the theoretical model establishes the validity of this explanation. ͓S0163-1829͑96͒03843-X͔

Magnetic quantum tunneling: insights from simple molecule-based magnets

“…This is essentially a classical result which reflects the fact that the uniform (in-phase) precession of N spins about a fixed axis is insensitive to the interactions between them, so long as the coupling is ferromagnetic and isotropic; this is analogous to Kohn's theorem for interacting electrons undergoing cyclotron motion. 67 On the basis of this result, the J independence of D 12 (red line, inset of Fig. 2) makes sense because it was inferred directly from D 0 /(2S -1).…”

Fast-electron magneto-optical spectrum of a two-dimensional electron gas in the presence of spin-orbit interaction and quantizing magnetic fields

“…1 In particular, fast-electron magneto-optical spectrum induced by electron-electron ͑e-e͒ interaction in a two-dimensional electron gas ͑2DEG͒ can be employed to study the effect of many-body interaction on important consequences such as the cyclotron resonance ͑CR͒ 2 and integer and fractional Landau-level ͑LL͒ occupancy. 3 It is known that when a 2DEG is subjected to a quantizing magnetic field and a polarized radiation field, the CR effect can be observed when the vector potential of the magnetic field couples to that of the radiation field, where a peak of optical absorption can be observed at ⍀ = c , with ⍀ the radiation frequency and c the cyclotron frequency. For a relatively high density 2DEG sample in which the correlation effect is weak, the CR effect depends rather weakly on the Zeeman spin splitting.…”