352 research outputs found
Sharp increase of the effective mass near the critical density in a metallic 2D electron system
We find that at intermediate temperatures, the metallic temperature
dependence of the conductivity \sigma(T) of 2D electrons in silicon is
described well by a recent interaction-based theory of Zala et al. (Phys. Rev.
B 64, 214204 (2001)). The tendency of the slope d\sigma/dT to diverge near the
critical electron density is in agreement with the previously suggested
ferromagnetic instability in this electron system. Unexpectedly, it is found to
originate from the sharp enhancement of the effective mass, while the effective
Lande g factor remains nearly constant and close to its value in bulk silicon
Photoluminescence rings in Corbino disk at quantizing magnetic fields
Spatially resolved photoluminescence of modulation doped AlGaAs/GaAs
heterojunction was investigated in a sample of Corbino disk geometry subject to
strong perpendicular magnetic fields. Significant spatial modulation of the
photoluminescence was observed in form of one or more concentric rings which
travelled across the sample when the magnetic field strength was varied. A
topology of the observed structure excludes the possibility of being a trace of
an external current. The effect is attributed to formation of compressible and
incompressible stripes in a 2DEG density gradient across the sample.Comment: 5 two-column pages, 4 figures (one of them in color
Spin susceptibility and polarization field in a dilute two-dimensional electron system in (111) silicon
We find that the polarization field, B_chi, obtained by scaling the
weak-parallel-field magnetoresistance at different electron densities in a
dilute two-dimensional electron system in (111) silicon, corresponds to the
spin susceptibility that grows strongly at low densities. The polarization
field, B_sat, determined by resistance saturation, turns out to deviate to
lower values than B_chi with increasing electron density, which can be
explained by filling of the upper electron subbands in the fully spin-polarized
regime
Metal-insulator transition in a 2D electron gas: Equivalence of two approaches for determining the critical point
The critical electron density for the metal-insulator transition in a
two-dimensional electron gas can be determined by two distinct methods: (i) a
sign change of the temperature derivative of the resistance, and (ii) vanishing
activation energy and vanishing nonlinearity of current-voltage characteristics
as extrapolated from the insulating side. We find that in zero magnetic field
(but not in the presence of a parallel magnetic field), both methods give
equivalent results, adding support to the existence of a true zero-field
metal-insulator transition.Comment: As publishe
- …