1,443 research outputs found
Electrical generation of pure spin currents in a two-dimensional electron gas
Pure spin currents are measured in micron-wide channels of GaAs
two-dimensional electron gas (2DEG). Spins are injected and detected using
quantum point contacts, which become spin polarized at high magnetic field.
High sensitivity to the spin signal is achieved in a nonlocal measurement
geometry, which dramatically reduces spurious signals associated with charge
currents. Measured spin relaxation lengths range from 30 to 50 microns, much
longer than has been reported in GaAs 2DEG's. The technique developed here
provides a flexible tool for the study of spin polarization and spin dynamics
in mesoscopic structures defined in 2D semiconductor systems
Physical phase space of lattice Yang-Mills theory and the moduli space of flat connections on a Riemann surface
It is shown that the physical phase space of \g-deformed Hamiltonian
lattice Yang-Mills theory, which was recently proposed in refs.[1,2], coincides
as a Poisson manifold with the moduli space of flat connections on a Riemann
surface with handles and therefore with the physical phase space of
the corresponding -dimensional Chern-Simons model, where and are
correspondingly a total number of links and vertices of the lattice. The
deformation parameter \g is identified with and is an
integer entering the Chern-Simons action.Comment: 12 pages, latex, no figure
Nuclear Polarization in Quantum Point Contacts in an In-Plane Magnetic Field
Nuclear spin polarization is typically generated in GaAs quantum point
contacts (QPCs) when an out-of-plane magnetic field gives rise to
spin-polarized quantum Hall edge states, and a voltage bias drives transitions
between the edge states via electron-nuclear flip-flop scattering. Here, we
report a similar effect for QPCs in an in-plane magnetic field, where currents
are spin polarized but edge states are not formed. The nuclear polarization
gives rise to hysteresis in the d.c. transport characteristics, with relaxation
timescales around 100 seconds. The dependence of anomalous QPC conductance
features on nuclear polarization provides a useful test of their
spin-sensitivity.Comment: 5 page
Disentangling the effects of spin-orbit and hyperfine interactions on spin blockade
We have achieved the few-electron regime in InAs nanowire double quantum
dots. Spin blockade is observed for the first two half-filled orbitals, where
the transport cycle is interrupted by forbidden transitions between triplet and
singlet states. Partial lifting of spin blockade is explained by spin-orbit and
hyperfine mechanisms that enable triplet to singlet transitions. The
measurements over a wide range of interdot coupling and tunneling rates to the
leads are well reproduced by a simple transport model. This allows us to
separate and quantify the contributions of the spin-orbit and hyperfine
interactions.Comment: 5 pages, 4 figure
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