Screening and edge states in two-dimensional metals in a magnetic field

Abstract

The length λ0 at which the lateral electric-field component E ⊥ perpendicular to the boundary is conserved near the boundary of two-dimensional (2D) samples, which is covered by 2D electrons, has been determined. The existence of the finite such length follows from the self-consistent process of the screening of the external fields forming the boundaries of real 2D systems by the electrons of the metal. The effect of E ⊥ on the structure of magnetic edge states has been taken into account in the mean field approximation in a wide range of the external field from the semiclassical limit (ɛF ≫ ħωc), where ɛF is the Fermi energy of the 2D system and ħωc is the cyclotron energy to the quantum Hall effect (QHE) region (ɛF ≪ ħωc). The positions of the magnetic edge state peaks against the background of their ideal distribution along the perimeter of the 2D circle in the known problem of transverse magnetic focusing have been determined in the semiclassical limit. The systematic description of the structure of the skin layer with λ H ≥ λ0, consisting of the set of the so-called integer strips (overlapping or independent), which are carriers of the universal quantum conductance, has been proposed in the QHE regime. A relatively large probability of the overlapping of the fields of adjacent strips, as well as the possibility of describing coupled integer cascades, is remarkable. The existing data on the tunneling current through integer strips in the λ H layer providing suitable information on the actual state of the boundary of the 2D system have been commented. A natural analogy between the properties of magnetic edge states and a well-known problem of the details of the ballistic conductance σ‖(H) of narrow electron channels in the magnetic field H has been noticed. The formalisms of both problems are identical under the conditions λ H ≥ w, where 2w is the effective width of the quasi-one-dimensional channel. The existing information on the σ‖(H) dependence in a wide range of the magnetic field has been systematized. The attributes of the QHE observed in σ‖(H) convincingly indicate the reality of the formation of various modifications of integer strips in inhomogeneous 2D systems in the quantizing magnetic field.