114 research outputs found
Gate-Controlled Electron Spin Resonance in a GaAs/AlGaAs Heterostructure
The electron spin resonance (ESR) of two-dimensional electrons is
investigated in a gated GaAs/AlGaAs heterostructure. We found that the ESR
resonance frequency can be turned by means of a gate voltage. The front and
back gates of the heterostructure produce opposite g-factor shift, suggesting
that electron g-factor is being electrostatically controlled by shifting the
equilibrium position of the electron wave function from one epitaxial layer to
another with different g-factors
Electron--Electron Scattering in Quantum Wires and it's Possible Suppression due to Spin Effects
A microscopic picture of electron-electron pair scattering in single mode
quantum wires is introduced which includes electron spin. A new source of
`excess' noise for hot carriers is presented. We show that zero magnetic field
`spin' splitting in quantum wires can lead to a dramatic `spin'-subband
dependence of electron--electron scattering, including the possibility of
strong suppression. As a consequence extremely long electron coherence lengths
and new spin-related phenomena are predicted. Since electron bands in III-V
semiconductor quantum wires are in general spin-split in zero applied magnetic
field, these new transport effects are of general importance.Comment: 11 pages, LaTeX and APS-RevteX 2, Rep.No. GF66,Figures from author,
Physical Review Letters, scheduled for 7 June 199
Zero-field spin splitting in InAs-AlSb quantum wells revisited
We present magnetotransport experiments on high-quality InAs-AlSb quantum
wells that show a perfectly clean single-period Shubnikov-de Haas oscillation
down to very low magnetic fields. In contrast to theoretical expectations based
on an asymmetry induced zero-field spin splitting, no beating effect is
observed. The carrier density has been changed by the persistent photo
conductivity effect as well as via the application of hydrostatic pressure in
order to influence the electric field at the interface of the electron gas.
Still no indication of spin splitting at zero magnetic field was observed in
spite of highly resolved Shubnikov- de Haas oscillations up to filling factors
of 200. This surprising and unexpected result is discussed in view of other
recently published data.Comment: 4 pages, 3 figures, submitted to Phys. Rev.
Conductance of a quantum point contact in the presence of spin-orbit interaction
A recursive Green's function technique is developed to calculate the
spin-dependent conductance in mesoscopic structures. Using this technique, we
study the spin-dependent electronic transport of quantum point contacts in the
presence of the Rashba spin-orbit interaction. We observed that some
oscillations in the `quantized' conductance are induced by the spin-orbit
interaction, and indicated that the oscillations may stem from the spin-orbit
coupling associated multiple reflections. It is also indicated that the 0.7
structure of the conductance observed in mesoscopic experiments would not stem
from the spin-orbit interaction.Comment: 8 page
Topological defects and Goldstone excitations in domain walls between ferromagnetic quantum Hall effect liquids
It is shown that the low-energy spectrum of a ferromagnetic quantum Hall
effect liquid in a system with a multi-domain structure generated by an
inhomogeneous bare Zeeman splitting is formed by excitations
localized at the walls between domains. For a step-like , the
domain wall spectrum includes a spin-wave with a linear dispersion and a small
gap due to spin-orbit coupling, and a low-energy topological defects. The
latter are charged and may dominate in the transport under conditions that the
percolation through the network of domain walls is provided.Comment: 4 pages, 1 fi
Dissipation effects in spin-Hall transport of electrons and holes
We investigate the spin-Hall effect of both electrons and holes in
semiconductors using the Kubo formula in the correct zero-frequency limit
taking into account the finite momentum relaxation time of carriers in real
semiconductors. This approach allows to analyze the range of validity of recent
theoretical findings. In particular, the spin-Hall conductivity vanishes for
vanishing spin-orbit coupling if the correct zero-frequency limit is performed.Comment: 5 pages, no figures, version to appear in Phys. Rev.
Spin-Orbit Interaction Enhanced Fractional Quantum Hall States in the Second Landau Level
We study the fractional quantum Hall effect at filling fractions 7/3 and 5/2
in the presence of the spin-orbit interaction, using the exact diagonalization
method and the density matrix renormalization group (DMRG) method in a
spherical geometry. Trial wave functions at these fillings are the Laughlin
state and the Moore-Reed-Pfaffian state. The ground state excitation energy
gaps and pair-correlation functions at fractional filling factor 7/3 and 5/2 in
the second Landau level are calculated. We find that the spin-orbit interaction
stabilizes the fractional quantum Hall states.Comment: 4pages, 4figure
Spin-orbit coupling effect on quantum Hall ferromagnets with vanishing Zeeman energy
We present the phase diagram of a ferromagnetic quantum Hall effect liquid in
a narrow quantum well with vanishing single-particle Zeeman splitting,
and pronounced spin-orbit coupling. Upon decreasing
, the spin-polarization field of a liquid takes, first, the
easy-axis configuration, followed by the formation of a helical state, which
affects the transport and NMR properties of a liquid and the form of
topological defects in it. The analysis is extended over high odd integer
filling factors.Comment: This revised version takes into account easy-axis terms in the energy
and offers a corrected phase diagram of the ferromagnetic QHE liquid.
Analysis is extended over higher filling factor
Filtering spin with tunnel-coupled electron wave guides
We show how momentum-resolved tunneling between parallel electron wave guides
can be used to observe and exploit lifting of spin degeneracy due to Rashba
spin-orbit coupling. A device is proposed that achieves spin filtering without
using ferromagnets or the Zeeman effect.Comment: 4 pages, 4 figures, RevTex
Spin Accumulation in Quantum Wires with Strong Rashba Spin-Orbit Coupling
We present analytical and numerical results for the effect of Rashba
spin-orbit coupling on band structure, transport, and interaction effects in
quantum wires when the spin precession length is comparable to the wire width.
In contrast to the weak-coupling case, no common spin-quantization axis can be
defined for eigenstates within a single-electron band. The situation with only
the lowest spin-split subbands occupied is particularly interesting because
electrons close to Fermi points of the same chirality can have approximately
parallel spins. We discuss consequences for spin-dependent transport and
effective Tomonaga-Luttinger descriptions of interactions in the quantum wire.Comment: 4 pages, 4 figures, expanded discussion of spin accumulatio
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