98 research outputs found
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.
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
Conduction band spin splitting and negative magnetoresistance in heterostructures
The quantum interference corrections to the conductivity are calculated for
an electron gas in asymmetric quantum wells in a magnetic field. The theory
takes into account two different types of the spin splitting of the conduction
band: the Dresselhaus terms, both linear and cubic in the wave vector, and the
Rashba term, linear in wave vector. It is shown that the contributions of these
terms into magnetoconductivity are not additive, as it was traditionally
assumed. While the contributions of all terms of the conduction band splitting
into the D'yakonov--Perel' spin relaxation rate are additive, in the
conductivity the two linear terms cancel each other, and, when they are equal,
in the absence of the cubic terms the conduction band spin splitting does not
show up in the magnetoconductivity at all. The theory agrees very well with
experimental results and enables one to determine experimentally parameters of
the spin-orbit splitting of the conduction band.Comment: 8 pages, RevTeX, 4 Postscript figure
Electron spin operation by electric fields: spin dynamics and spin injection
Spin-orbit interaction couples electron spins to electric fields and allows
electrical monitoring of electron spins and electrical detection of spin
dynamics. Competing mechanisms of spin-orbit interaction are compared, and
optimal conditions for the electric operation of electrons spins in a quantum
well by a gate voltage are established. Electric spin injection into
semiconductors is discussed with a special emphasis on the injection into
ballistic microstructures. Dramatic effect of a long range Coulomb interaction
on transport phenomena in space-quantized low-dimensional conductors is
discussed in conclusion.Comment: A plenary paper at the 11th Intern. Conf. on Narrow Gap
Semiconductors (Buffalo, NY, June 2003). To be published in Physica
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
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
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
Theory of electrical spin injection: Tunnel contacts as a solution of the conductivity mismatch problem
Theory of electrical spin injection from a ferromagnetic (FM) metal into a
normal (N) conductor is presented. We show that tunnel contacts (T) can
dramatically increase spin injection and solve the problem of the mismatch in
the conductivities of a FM metal and a semiconductor microstructure. We also
present explicit expressions for the spin-valve resistance of FM-T-N- and
FM-T-N-T-FM-junctions with tunnel contacts at the interfaces and show that the
resistance includes both positive and negative contributions (Kapitza
resistance and injection conductivity, respectively).Comment: 4 pages, to appear in Phys. Rev. B (rapid communications
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
Interference of Spin Splittings in Magneto-Oscillation Phenomena in Two-Dimensional Systems
The spin splitting caused by the terms linear in wavevector in the effective
Hamiltonian containing can give rise to the new magneto-oscillation phenomena
in two-dimensional systems. It is shown that the joint action of the
spin-dependent contributions due to the heterostructure asymmetry and to the
lack of inversion center in the bulk material suppresses beats that arise in
the magneto-oscillation phenomena in the presence of the terms of only one of
these types.Comment: pdf file, 4 pages, 2 figure
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