Resonant Subband Landau Level Coupling Research Articles

Resonant subband Landau level coupling in symmetric quantum well

Subband structure and depolarization shifts in an ultrahigh mobility GaAs/Al0.24Ga0.76As quantum well are studied using magnetoinfrared spectroscopy via resonant subband Landau level coupling. Resonant couplings between the first and up to the fourth subbands are identified by well-separated antilevel-crossing split resonance, while the hy-lying subbands were identified by the cyclotron resonance linewidth broadening in the literature. In addition, a forbidden intersubband transition (first to third) has been observed. With the precise determination of the subband structure, we find that the depolarization shift can be well described by the semiclassical slab plasma model and the possible origins for the forbidden transition are discussed.

In-plane and perpendicular magnetic fields dependence of cyclotron resonance in two-dimensional electron systems

The cyclotron resonance of two-dimensional electron systems (2DES) of GaAs/AlGaAs heterostructures is investigated in a tilted magnetic field. In this study, the perpendicular ( B ⊥) and in-plane ( B ||) magnetic fields are changed systematically. More than two cyclotron resonances caused by B || are observed. Further, the enhancement of cyclotron mass by B || and its dependence on B ⊥ and electron concentration of 2DES are also investigated in detail. These phenomena are well explained by the resonant subband Landau level coupling model.

The influence of electron–electron interactions on cyclotron resonance in subband-Landau level coupling systems

We investigate the influence of electron–electron interactions on cyclotron resonance (CR) of two-dimensional electron systems in tilted magnetic field. It is known that the electron–electron interactions affect the CR spectra in systems that have more than two cyclotron frequencies. In this study, this multi-component system is realized by applying the tilted magnetic field; the tilted magnetic field induces the resonant subband-Landau level coupling (RSLC) and a splitting of the CR spectrum is observed. Observed anomalous CR spectra cannot be explained by the RSLC with the single-electron picture. Present theoretical treatments cannot account for the result of our experiment.

Cyclotron resonance of ultrashort-period lateral superlattices

The cyclotron resonance of laterally modulated two-dimensional electron systems grown on (775)B-oriented GaAs substrates is measured. The lateral period of this structure is ultrashort, 12 nm. Observed cyclotron resonance spectra show the anticrossing behavior or more complicated behavior. It is found that the behavior cannot be explained by the Landau bands formation and the resonant subband-Landau level coupling that is induced by the potential modulation. A possible explanation for the behavior is the effect of electron–electron interactions introduced by breakdown of translational invariance.

RESONANT SUBBAND-LANDAU-LEVEL COUPLING FOR HIGH-LYING SUBBANDS OF TWO-DIMENSIONAL ELECTRON GASES IN GaAs/AlGaAs HETEROJUNCTION

The resonant subband-Landau-level coupling(RSLC) between the N=1 Landau level of the lowest subband and the N＝0 Landau level of the subbands with quantum index up to i＝5 of two-dimensional electron gases in GaAs/AlGaAs heterojunction was observed under relatively low magnetic field.Several intersubband energies were accurately determined. The experimental results were in good agreement with the self-consistent calculations including the depolarization shift and exciton-like effect corrections.The quantum index dependence of the level splitting due to the RSLC was discussed.

High-lying thermally excited subbands of two-dimensional electron gases in GaAs/AlGaAs heterojunction for modulation-doped field-effect transistor

The cyclotron resonance of two-dimensional electron gases was directly measured on a modulation-doped field-effect transistor structure by the gate voltage ratio spectroscopy. The intersubband energies between the lowest subband and the subbands with quantum index up to i=5 were determined by resonant subband-Landau-level coupling (RSLC) under relatively low magnetic field. The experimental results were in good agreement with the self-consistent calculations including the depolarization shift and exciton-like effect corrections. The quantum index dependence of the level splitting due to the RSLC was discussed.

Resonant Subband-Landau Level Coupling in Systems with Anisotropic and Tilted Valleys

The problem of the anticrossing of the Landau 1evels originating from the ground subband and first excited subband in the quasi-two-dimensional systems with anisotropic valleys in the presence of the tilted magnetic field is discussed in the framework of the perturbation theory. The full field coupling regime is considered. Comparison with the existing theoretical and experimental results is given.

Determination of subband structure, depolarization shift, and depletion charge in an AlxGa1-xAs-GaAs heterostructure.

Resonant subband-Landau-level coupling (RSLC) spectroscopy is applied to study intersubband-resonance excitations in ${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As-GaAs heterostructures. The carrier density ${N}_{s}$ in our device can be tuned via a front gate voltage ${V}_{g}$ in a controlled and reproducible way. The detailed analysis of the ${N}_{s}$ dependence of the intersubband resonance and the comparison with a self-consistent calculation demonstrate that the anti-level-crossing in the RSLC experiment occurs at an energy E${\ifmmode \tilde{}\else \~{}\fi{}}_{10}$ which is shifted by the collective depolarization effect with respect to the subband separation ${E}_{10}$. From the same analysis we can also determine the depletion charge ${N}_{\mathrm{depl}}$ with an accuracy of 5%. This gives us the possibility to distinguish between a persistent photoeffect upon illumination arising first from carriers out of the GaAs buffer layer and later on from the doped ${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As region.