80 research outputs found
Electrical Detection of Spin Accumulation at a Ferromagnet-Semiconductor Interface
We show that the accumulation of spin-polarized electrons at a forward-biased
Schottky tunnel barrier between Fe and n-GaAs can be detected electrically. The
spin accumulation leads to an additional voltage drop across the barrier that
is suppressed by a small transverse magnetic field, which depolarizes the spins
in the semiconductor. The dependence of the electrical accumulation signal on
magnetic field, bias current, and temperature is in good agreement with the
predictions of a drift-diffusion model for spin-polarized transport.Comment: Submitted to Phys. Rev. Let
Spin injection from perpendicular magnetized ferromagnetic -MnGa into (Al,Ga)As heterostructures
Electrical spin injection from ferromagnetic -MnGa into an (Al,Ga)As
p-i-n light emitting diode (LED) is demonstrated. The -MnGa layers show
strong perpendicular magnetocrystalline anisotropy, enabling detection of spin
injection at remanence without an applied magnetic field. The bias and
temperature dependence of the spin injection are found to be qualitatively
similar to Fe-based spin LED devices. A Hanle effect is observed and
demonstrates complete depolarization of spins in the semiconductor in a
transverse magnetic field.Comment: 4 pages, 3 figure
Spin injection from the Heusler alloy Co_2MnGe into Al_0.1Ga_0.9As/GaAs heterostructures
Electrical spin injection from the Heusler alloy Co_2MnGe into a p-i-n
Al_0.1Ga_0.9As/GaAs light emitting diode is demonstrated. A maximum
steady-state spin polarization of approximately 13% at 2 K is measured in two
types of heterostructures. The injected spin polarization at 2 K is calculated
to be 27% based on a calibration of the spin detector using Hanle effect
measurements. Although the dependence on electrical bias conditions is
qualitatively similar to Fe-based spin injection devices of the same design,
the spin polarization injected from Co_2MnGe decays more rapidly with
increasing temperature.Comment: 8 pages, 4 figure
Quantized conductance doubling and hard gap in a two-dimensional semiconductor-superconductor heterostructure
The prospect of coupling a two-dimensional (2D) semiconductor heterostructure
to a superconductor opens new research and technology opportunities, including
fundamental problems in mesoscopic superconductivity, scalable superconducting
electronics, and new topological states of matter. For instance, one route
toward realizing topological matter is by coupling a 2D electron gas (2DEG)
with strong spin-orbit interaction to an s-wave superconductor. Previous
efforts along these lines have been hindered by interface disorder and unstable
gating. Here, we report measurements on a gateable InGaAs/InAs 2DEG with
patterned epitaxial Al, yielding multilayer devices with atomically pristine
interfaces between semiconductor and superconductor. Using surface gates to
form a quantum point contact (QPC), we find a hard superconducting gap in the
tunneling regime, overcoming the soft-gap problem in 2D
superconductor-semiconductor hybrid systems. With the QPC in the open regime,
we observe a first conductance plateau at 4e^2/h, as expected theoretically for
a normal-QPC-superconductor structure. The realization of a hard-gap
semiconductor-superconductor system that is amenable to top-down processing
provides a means of fabricating scalable multicomponent hybrid systems for
applications in low-dissipation electronics and topological quantum
information.Comment: includes main text, supplementary information and code for
simulations. Published versio
Semimetalic antiferromagnetism in the half-Heusler compound CuMnSb
The half-Heusler compound CuMnSb, the first antiferromagnet (AFM) in the
Mn-based class of Heuslers and half-Heuslers that contains several conventional
and half metallic ferromagnets, shows a peculiar stability of its magnetic
order in high magnetic fields. Density functional based studies reveal an
unusual nature of its unstable (and therefore unseen) paramagnetic state, which
for one electron less (CuMnSn, for example) would be a zero gap semiconductor
(accidentally so) between two sets of very narrow, topologically separate bands
of Mn 3d character. The extremely flat Mn 3d bands result from the environment:
Mn has four tetrahedrally coordinated Cu atoms whose 3d states lie well below
the Fermi level, and the other four tetrahedrally coordinated sites are empty,
leaving chemically isolated Mn 3d states. The AFM phase can be pictured
heuristically as a self-doped CuMnSb compensated semimetal
with heavy mass electrons and light mass holes, with magnetic coupling
proceeding through Kondo and/or antiKondo coupling separately through the two
carrier types. The ratio of the linear specific heat coefficient and the
calculated Fermi level density of states indicates a large mass enhancement
, or larger if a correlated band structure is taken as the
reference
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