236 research outputs found
Local spin valve effect in lateral (Ga,Mn)As/GaAs spin Esaki diode devices
We report on a local spin valve effect observed unambiguously in lateral
all-semiconductor all-electrical spin injection devices, employing
p+-(Ga,Mn)As/n+-GaAs Esaki diode structures as spin aligning contacts. We
discuss the observed local spin-valve signal as a result of interplay between
spin-transport-related contribution and tunneling anisotropic magnetoresistance
of magnetic contacts. The magnitude of the spin-related magnetoresistance
change is equal to 30 Ohm which is twice the magnitude of the measured
non-local signal.Comment: submitted to Appl. Phys. Let
Tunneling Anisotropic Spin Polarization in lateral (Ga,Mn)As/GaAs spin Esaki diode devices
We report here on anisotropy of spin polarization obtained in lateral
all-semiconductor all-electrical spin injection devices, employing
(Ga,Mn)As/GaAs Esaki diode structures as spin aligning
contacts, resulting from the dependence of the efficiency of spin tunneling on
the orientation of spins with respect to different crystallographic directions.
We observed an in-plane anisotropy of in case of spins oriented either
along or directions and anisotropy between
in-plane and perpendicular-to-plane orientation of spins.Comment: 9 pages, 3 figure
All-electrical measurements of direct spin Hall effect in GaAs with Esaki diode electrodes
We report on measurements of direct spin Hall effect in a lightly n-doped
GaAs channel. As spin detecting contacts we employed highly efficient
ferromagnetic Fe/(Ga,Mn)As/GaAs Esaki diode structures. We investigate bias and
temperature dependence of the measured spin Hall signal and evaluate the value
of total spin Hall conductivity and its dependence on channel conductivity and
temperature. From the results we determine skew scattering and side jump
contribution to the total spin hall conductivity and compare it with the
results of experiments on higher conductive n-GaAs channels[Phys. Rev. Lett.
105,156602(2010)]. As a result we conclude that both skewness and side jump
contribution cannot be fully independent on the conductivity of the channel.Comment: 14 pages, 4 figure
Controlling hole spin dynamics in two‐dimensional hole systems at low temperatures
With the recent discovery of very long hole spin decoherence times in GaAs/AlGaAs heterostructures of more than 70 ns
in two-dimensional hole systems, using the hole spin as a viable alternative to electron spins in spintronic applications seems
possible. Furthermore, as the hyperfine interaction with the nuclear spins is likely to be the limiting factor for electron spin
lifetimes in zero dimensions, holes with their suppressed Fermi contact hyperfine interaction due to their p-like nature should
be able to show even longer lifetimes than electrons. For spintronic applications, electric-field control of hole spin dynamics
is desirable.
Here, we report on time-resolved Kerr rotation and resonant spin amplification measurements on a two-dimensional hole
system in a p-doped GaAs/AlGaAs heterostructure. Via a semitransparent gate, we tune the charge density within the sample.
We are able to observe a change in the hole g factor, as well as in the hole spin dephasing time at high magnetic fields
Multistability and spin diffusion enhanced lifetimes in dynamic nuclear polarization in a double quantum dot
The control of nuclear spins in quantum dots is essential to explore their
many-body dynamics and exploit their prospects for quantum information
processing. We present a unique combination of dynamic nuclear spin
polarization and electric-dipole-induced spin resonance in an electrostatically
defined double quantum dot (DQD) exposed to the strongly inhomogeneous field of
two on-chip nanomagnets. Our experiments provide direct and unrivaled access to
the nuclear spin polarization distribution and allow us to establish and
characterize multiple fixed points. Further, we demonstrate polarization of the
DQD environment by nuclear spin diffusion which significantly stabilizes the
nuclear spins inside the DQD
Resonant spin amplification of hole spin dynamics in two‐dimensional hole systems: experiment and simulation
Spins in semiconductor structures may allow for the realization of scalable quantum bit arrays, an essential
component for quantum computation schemes. Specifically, hole spins may be more suited for this purpose than electron
spins, due to their strongly reduced interaction with lattice nuclei, which limits spin coherence for electrons in quantum dots.
Here, we present resonant spin amplification (RSA) measurements, performed on a p-modulation doped GaAs-based quantum
well at temperatures below 500 mK. The RSA traces have a peculiar, butterfly-like shape, which stems from the initialization
of a resident hole spin polarization by optical orientation. The combined dynamics of the optically oriented electron and hole
spins are well-described by a rate equation model, and by comparison of experiment and model, hole spin dephasing times of
more than 70 ns are extracted from the measured data
Large nuclear spin polarization in gate-defined quantum dots using a single-domain nanomagnet
The electron-nuclei (hyperfine) interaction is central to spin qubits in
solid state systems. It can be a severe decoherence source but also allows
dynamic access to the nuclear spin states. We study a double quantum dot
exposed to an on-chip single-domain nanomagnet and show that its inhomogeneous
magnetic field crucially modifies the complex nuclear spin dynamics such that
the Overhauser field tends to compensate external magnetic fields. This turns
out to be beneficial for polarizing the nuclear spin ensemble. We reach a
nuclear spin polarization of ~50%, unrivaled in lateral dots, and explain our
manipulation technique using a comprehensive rate equation model
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