Spin polarization in modulation-dopedGaAsquantum wires

Abstract

We study spin polarization in a split-gate quantum wire focusing on the effect of a realistic smooth potential due to remote donors. Electron interaction and spin effects are included within the density functional theory in the local spin density approximation. We find that depending on the electron density, the spin polarization exhibits qualitatively different features. For the case of relatively high electron density, when the Fermi energy E F exceeds a characteristic strength of a long-range impurity potential V donors , the density spin polarization inside the wire is practically negligible and the wire conductance is spin-degenerate. When the density is decreased such that E F approaches V donors , the electron density and conductance quickly become spin polarized. With further decrease of the density the electrons are trapped inside the lakes ͑droplets͒ formed by the impurity potential and the wire conductance approaches the pinch-off regime. We discuss the limitations of the density functional theory in the local spin density approximation in this regime and compare the obtained results with available experimental data.

Oscillatory Hall effect in high-mobility two-dimensional electron gases

“…4,5 However, despite much work, both nature and origin of the exchange interaction that drives the spin polarization remains widely debated. Two mechanisms are generally cited in literature: many-body exchange arising from Coulomb interaction at low carrier densities, [6][7][8][9] and the possibility of a Kondo effect by virtual bound states or by localized spins in confined mesoscopic systems. [10][11][12] For the latter case it was suggested that a many-body spin polarization arises from an indirect Ruderman-Kittel-Kasuya-Yosida ͑RKKY͒ exchange, 5 which can be tuned with gate voltage in an oscillatory manner.…”

Interaction-induced enhancement ofgfactor in graphene

“…[7][8][9][10][11][12][13][14][15] It was also argued that interaction-induced spontaneous spin splitting can take place in 2DEG systems even in the absence of a magnetic field. [16][17][18] The enhancement of the effective g factor was also observed in carbon-based systems. In graphite the effective g factor is reported to be g * ≈ 2.5.…”

Role of Edge Geometry and Magnetic Interaction in Opening Bandgap of Low‐Dimensional Graphene

“…In Figure 3 A, our predicted E g (D) curves are in agreement with the semiconducting state (symbols) predicted by the DFT method, [26,[55][56][57] but different from the predicted metallic state with E g (D) = 0 eV using the TB method because of the localized state at the Fermi level. [39,41,42] In fact, the met-allic or semiconducting state reported for ZZ-GNRs has also been reflected with some simple sine or cosine functions. The difference in the BOs observed there is ascribed to the role of edge saturation by H, which generates localized edge states by the TB method [41,42] but results in the bandgap expansion by the DFT method.…”

“…[39,41,42] In fact, the met-allic or semiconducting state reported for ZZ-GNRs has also been reflected with some simple sine or cosine functions. The difference in the BOs observed there is ascribed to the role of edge saturation by H, which generates localized edge states by the TB method [41,42] but results in the bandgap expansion by the DFT method. [23,43] To see how E m g (D) and E a g (D) contribute to E g (D) of ZZ-GNRs, the functions of E a g (D) and E m g (D) are further plotted in Figure 3 with dashed curves.…”

“…The oscillating metallic and semiconducting state [23] (or the full semiconducting state [21] ) of AC-GNRs is depicted with several successions of sine/cosine functions [or a fitting expression of E g (D) = a/D b [25] ]. The metallic state [41,42] (or the semiconducting state [23,43] ) of ZZ-GNRs is usually described with E g (D) = By using a size-dependent cohesive energy formula for two-dimensional coordination materials, the bandgap openings of ideal graphene quantum dots (GQDs) and nanoribbons (GNRs) have been investigated systematically regarding dimension, edge geometry, and magnetic interaction. Results demonstrate that the bandgap openings in GQDs can be dominated by the change of atomic cohesive energy.…”