Cyclotron effective mass of a two-dimensional electron layer at the GaAs/AlxGa1

Abstract

We have found that Fermi contours of a two-dimensional electron gas at GaAs/AlxGa1−xAs interface deviate from a standard circular shape under the combined influence of an approximately triangular confining potential and the strong in-plane magnetic field. The distortion of a Fermi contour manifests itself through an increase of the electron effective cyclotron mass which has been measured by the cyclotron resonance in the far-infrared transmission spectra and by the thermal damping of Shubnikov-de Haas oscillations in tilted magnetic fields with an in-plane component up to 5 T. The observed increase of the cyclotron effective mass reaches almost 5 % of its zero field value which is in good agreement with results of a self-consistent calculation. 72.40, 72.20

Orbital effect of an in-plane magnetic field on quantum transport in chaotic lateral dots

“…The Lorentz force generated by a planar field on electrons moving across B within the 2D plane mixes up the electron motion along and across the confinement direction, thus resulting in the electron momentum, p dependent subband mixing and, therefore, in a modification of the 2D dispersion, E(p) → E( B , p). In particular, (a) the 2D electron mass increases in the direction perpendicular to B , whereas (b) in heterostructures which have no inversion symmetry in the form of confining potential, B also lifts the p → − p symmetry in the dispersion law [11]:The latter change in dispersion has potential to reduce the fundamental symmetry of chaotic dot from orthogonal (o) to unitary (u), as a perpendicular magnetic field would do. Below, we show that the efficiency of timereversal symmetry breaking by an in-plane magnetic field can be characterized using the rate τ −1 B ∼ bB 6 + aB 2 described in Eq.…”

“…Two additional terms in the free electron dispersion part ofĤ 2D are the result of the p ⊥ -dependent inter-subband mixing. The first of them lifts rotational symmetry by causing an anisotropic mass enhancement [11]. It increases the 2D density of states and, for a 2D gas with a fixed sheet density, it reduces the Fermi energy calculated from the bottom of the 2D conduction band, E F (B ) = E 0 F − γ(B ) 2 p 2 F .…”

“…The Lorentz force generated by a planar field on electrons moving across B within the 2D plane mixes up the electron motion along and across the confinement direction, thus resulting in the electron momentum, p dependent subband mixing and, therefore, in a modification of the 2D dispersion, E(p) → E( B , p). In particular, (a) the 2D electron mass increases in the direction perpendicular to B , whereas (b) in heterostructures which have no inversion symmetry in the form of confining potential, B also lifts the p → − p symmetry in the dispersion law [11]:…”

“…This feature has also been accompanied by an observation [10] of such a negative weak localisation (WL) magnetoresistance caused by an in-plane field B that one would relate to the time-reversal symmetry breaking in the orbital motion of electrons. In the present publication, we assess to which extent one can reduce the influence of an ideally in-plane tuned magnetic field on quantum transport in lateral semiconductor dots to spin effects alone, that is, we determine the range of fields B that would affect WL and UCF's in experimentally studied devices [4], in addition to spin-related phenomena.The influence of an in-plane magnetic field on the orbital motion of carriers in a heterostructure or quantum well is the result of a finite width, λ z of a 2D layer, and it has been discussed previously in various contexts [11,12]. The Lorentz force generated by a planar field on electrons moving across B within the 2D plane mixes up the electron motion along and across the confinement direction, thus resulting in the electron momentum, p dependent subband mixing and, therefore, in a modification of the 2D dispersion, E(p) → E( B , p).…”

“…The influence of an in-plane magnetic field on the orbital motion of carriers in a heterostructure or quantum well is the result of a finite width, λ z of a 2D layer, and it has been discussed previously in various contexts [11,12]. The Lorentz force generated by a planar field on electrons moving across B within the 2D plane mixes up the electron motion along and across the confinement direction, thus resulting in the electron momentum, p dependent subband mixing and, therefore, in a modification of the 2D dispersion, E(p) → E( B , p).…”