Hysteresis and defects of spin-polarized edge states in the integer quantum Hall regime

Abstract

The magnetic con6guration of edge channels near the boundary of a quasi-two-dimensional electron gas in the integer quantum Hall regime is studied in the Hartree-Fock approximation. In earlier work [J. Dempsey, B.Y. Gelfand, and B.I. Halperin, Phys. Rev. Lett. 'FO, 3639 (1993)] electronelectron interactions were found to cause a spin-polarizing transition of the outermost edge states. These calculations are extended by including a nonequilibrium occupation of spin levels. A sudden reversal of edge-channel positions is predicted at values of the chemical-potential difference much smaller than the enhanced spin splitting at the edges. The crossings, which arise when edge channels switch position in open systems, are identi6ed as solitonlike, one-dimensional magnetic domain walls. The interaction between these magnetic defects is investigated. Possible consequences and veri6cation by experiment of the predictions are discussed.

Dynamic nuclear polarization at the edge of a two-dimensional electron gas

“…These effects have been predicted to manifest themselves at the edge as well, particularly in the neighborhood of the ν = 1 incompressible strip. One theory of the spin-split edge [31] predicts that the spin gap in this region can be enhanced by as much as a factor of 50. Our measurements of this gap (through the threshold voltage V t ) appear to indicate otherwise-the spin gap is only slightly enhanced (g*∼ 1.5g)-but this conclusion is based upon the assumption that V t and g* µ B B are directly related.…”

“…One theory [31] of spin-split edge states predicts hysteresis due entirely to electron-electron interactions. At a critical potential imbalance ∆µ + cr , the edge channels are predicted to switch positions, remaining in this switched orientation until a different potential difference ∆µ − cr is reached.…”

Coulomb effects on the quantum transport of a two-dimensional electron system in periodic electric and magnetic fields

“…This spin polarization of the edge states may occur spontaneously even if the bare g-factor vanishes, and has been discussed as a type of phase transition. [20][21][22] We believe that the occurrence of this spontaneous spin polarization is an artifact of the unscreened HFA, since our SHFA yields (as long as a ≫ l) only a very smooth and gradual reduction of the spin splitting with increasing modulation strength, with compressible spin polarized strips (energies pinned to the Fermi energy) instead of incompressible ones.…”

Separately contacted edge states at high imbalance in the integer and fractional quantum Hall effect regime

“…Such intersections were called defects in the topological structure of edge states, or topo- Figure 7 Simplest example of the topological defects in the edge states structure (after Ref. [29]). logical defects.…”