2,167 research outputs found
Low-dimensional light-emitting transistor with tunable recombination zone
We present experimental and numerical studies of a light-emitting transistor
comprising two quasi-lateral junctions between a two-dimensional electron and
hole gas. These lithographically defined junctions are fabricated by etching of
a modulation doped GaAs/AlGaAs heterostructure. In this device electrons and
holes can be directed to the same area by drain and gate voltages, defining a
recombination zone tunable in size and position. It could therefore provide an
architecture for probing low-dimensional devices by analysing the emitted light
of the recombination zone.Comment: 12 Pages, to be published in Journal of Modern Optic
Fast optical control of spin in semiconductor interfacial structures
We report on a picosecond-fast optical removal of spin polarization from a
self-confined photo-carrier system at an undoped GaAs/AlGaAs interface
possessing superior long-range and high-speed spin transport properties. We
employed a modified resonant spin amplification technique with unequal
intensities of subsequent pump pulses to experimentally distinguish the
evolution of spin populations originating from different excitation laser
pulses. We demonstrate that the density of spins, which is injected into the
system by means of the optical orientation, can be controlled by reducing the
electrostatic confinement of the system using an additional generation of
photocarriers. It is also shown that the disturbed confinement recovers within
hundreds of picoseconds after which spins can be again photo-injected into the
system
Fabrication and electrical transport properties of embedded graphite microwires in a diamond matrix
Micrometer width and nanometer thick wires with different shapes were
produced \approx 3~\upmum below the surface of a diamond crystal using a
microbeam of He ions with 1.8~MeV energy. Initial samples are amorphous and
after annealing at ~K, the wires crystallized into a
graphite-like structures, according to confocal Raman spectroscopy
measurements. The electrical resistivity at room temperature is only one order
of magnitude larger than the in-plane resistivity of highly oriented pyrolytic
bulk graphite and shows a small resistivity ratio(). A small negative magnetoresistance below ~K was
measured and can be well understood taking spin-dependent scattering processes
into account. The used method provides the means to design and produce
millimeter to micrometer sized conducting circuits with arbitrary shape
embedded in a diamond matrix.Comment: 12 pages, 5 figures, to be published in Journal of Physics D: Applied
Physics (Feb. 2017
Quantum gates using electronic and nuclear spins of Yb in a magnetic field gradient
An efficient scheme is proposed to carry out gate operations on an array of
trapped Yb ions, based on a previous proposal using both electronic and
nuclear degrees of freedom in a magnetic field gradient. For this purpose we
consider the Paschen-Back regime (strong magnetic field) and employ a
high-field approximation in this treatment. We show the possibility to suppress
the unwanted coupling between the electron spins by appropriately swapping
states between electronic and nuclear spins. The feasibility of generating the
required high magnetic field is discussed
Edge spin accumulation in semiconductor two-dimensional hole gases
The controlled generation of localized spin densities is a key enabler of
semiconductor spintronics In this work, we study spin Hall effect induced edge
spin accumulation in a two-dimensional hole gas with strong spin orbit
interactions. We argue that it is an intrinsic property, in the sense that it
is independent of the strength of disorder scattering. We show numerically that
the spin polarization near the edge induced by this mechanism can be large, and
that it becomes larger and more strongly localized as the spin-orbit coupling
strength increases, and is independent of the width of the conducting strip
once this exceeds the elastic scattering mean-free-path. Our experiments in
two-dimensional hole gas microdevices confirm this remarkable spin Hall effect
phenomenology. Achieving comparable levels of spin polarization by external
magnetic fields would require laboratory equipment whose physical dimensions
and operating electrical currents are million times larger than those of our
spin Hall effect devices.Comment: 6 pages, 5 figure
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