308 research outputs found
Spin Polarization Phenomena and Pseudospin Quantum Hall Ferromagnetism in the HgTe Quantum Well
The parallel field of a full spin polarization of the electron gas in a
\Gamma8 conduction band of the HgTe quantum well was obtained from the
magnetoresistance by three different ways in a zero and quasi-classical range
of perpendicular field component Bper. In the quantum Hall range of Bper the
spin polarization manifests in anticrossings of magnetic levels, which were
found to strongly nonmonotonously depend on Bper.Comment: to be published in AIP Conf. Proc.: 15-th International Conference on
Narrow Gap Systems (NGS-15
Magnetotransport in Double Quantum Well with Inverted Energy Spectrum: HgTe/CdHgTe
We present the first experimental study of the double-quantum-well (DQW)
system made of 2D layers with inverted energy band spectrum: HgTe. The
magnetotransport reveals a considerably larger overlap of the conduction and
valence subbands than in known HgTe single quantum wells (QW), which may be
regulated by an applied gate voltage . This large overlap manifests itself
in a much higher critical field separating the range above it where the
quantum peculiarities shift linearly with and the range below with a
complicated behavior. In the latter case the -shaped and double--shaped
structures in the Hall magnetoresistance are observed with their
scale in field pronouncedly enlarged as compared to the pictures observed in an
analogous single QW. The coexisting electrons and holes were found in the whole
investigated range of positive and negative as revealed from fits to the
low-field -shaped and from the Fourier analysis of
oscillations in . A peculiar feature here is that the found
electron density remains almost constant in the whole range of investigated
while the hole density drops down from the value a factor of 6 larger
than at extreme negative to almost zero at extreme positive
passing through the charge neutrality point. We show that this difference
between and stems from an order of magnitude larger density of states
for holes in the lateral valence band maxima than for electrons in the
conduction band minimum. We interpret the observed reentrant sign-alternating
between electronic and hole conductivities and its zero
resistivity state in the quantum Hall range of fields on the basis of a
calculated picture of magnetic levels in a DQW.Comment: 15 pages, 13 figure
Effect of exchange electron-electron interaction on conductivity of InGaAs single and double quantum wells in ballistic regime
We report an experimental study of quantum conductivity corrections for
two-dimensional electron gas in a GaAs/InGaAs/GaAs single and double quantum
wells in a wide temperature range (1.8-100) K. We perform a comparison of our
experimental data for the longitudinal conductivity at zero magnetic field to
the theory of interaction-induced corrections to th transport coefficients. In
the temperature range from 10 K up to (45-60) K, wich covers the ballistic
interaction regimes for our samples, a rather good agreement between the theory
and our experimental results has been found
Effects of spin polarization in the HgTe quantum well
Magnetoresistivity features connected with the spin level coincidences under tilted fields in a Γ 8 conduction band of the HgTe quantum well were found to align along straight trajectories in a (B ⊥,B) plane between the field components perpendicular and parallel to the layer, meaning a linear spin polarization dependence on a magnetic field. Among the trajectories is a noticeable set of lines descending from a single point on the Baxis, which is shown to yield a field of the full spin polarization of the electronic system, in agreement with the data on the electron redistribution between spin subbands obtained from Fourier transforms of oscillations along circle trajectories in the (B ⊥,B) plane and with the point on the magnetoresistivity under pure Bseparating a complicated weak field dependence from the monotonous one. The whole picture of coincidences is well described by the isotropic g factor, although its value is twice as small as that obtained from oscillations under pure perpendicular fields. The discrepancy is attributed to different manifestations of spin polarization phenomena in the coincidences and within the exchange-enhanced spin gaps. In the quantum Hall range of B ⊥, the spin polarization manifests in anticrossings of magnetic levels, which were found to depend dramatically nonmonotonously on B ⊥. © 2012 American Physical Society
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