2,051 research outputs found
Spin gating electrical current
We use an aluminium single electron transistor with a magnetic gate to
directly quantify the chemical potential anisotropy of GaMnAs materials.
Uniaxial and cubic contributions to the chemical potential anisotropy are
determined from field rotation experiments. In performing magnetic field sweeps
we observe additional isotropic magnetic field dependence of the chemical
potential which shows a non-monotonic behavior. The observed effects are
explained by calculations based on the kinetic
exchange model of ferromagnetism in GaMnAs. Our device inverts the conventional
approach for constructing spin transistors: instead of spin-transport
controlled by ordinary gates we spin-gate ordinary charge transport.Comment: 5 pages, 4 figure
Anomalous Hall effect and weak localization corrections in a ferromagnet
In this paper, we report results on the anomalous Hall effect. First, we
summarize analytical calculations based on the Kubo formalism : explicit
expressions for both skew-scattering and side-jump are derived and
weak-localization corrections are discussed. Next, we present numerical
calculations of the anomalous Hall resistivity based on the Dirac equation.
Qualitative agreement with experiments is obtained.Comment: Proceeding JEMS'0
Spin Hall effect transistor
Spin transistors and spin Hall effects have been two separate leading
directions of research in semiconductor spintronics which seeks new paradigms
for information processing technologies. We have brought the two directions
together to realize an all-semiconductor spin Hall effect transistor. Our
scheme circumvents semiconductor-ferromagnet interface problems of the original
Datta-Das spin transistor concept and demonstrates the utility of the spin Hall
effects in microelectronics. The devices use diffusive transport and operate
without electrical current, i.e., without Joule heating in the active part of
the transistor. We demonstrate a spin AND logic function in a semiconductor
channel with two gates. Our experimental study is complemented by numerical
Monte Carlo simulations of spin-diffusion through the transistor channel.Comment: 11 pages, 3 figure
Spin-dependent phenomena and device concepts explored in (Ga,Mn)As
Over the past two decades, the research of (Ga,Mn)As has led to a deeper
understanding of relativistic spin-dependent phenomena in magnetic systems. It
has also led to discoveries of new effects and demonstrations of unprecedented
functionalities of experimental spintronic devices with general applicability
to a wide range of materials. In this article we review the basic material
properties that make (Ga,Mn)As a favorable test-bed system for spintronics
research and discuss contributions of (Ga,Mn)As studies in the general context
of the spin-dependent phenomena and device concepts. Special focus is on the
spin-orbit coupling induced effects and the reviewed topics include the
interaction of spin with electrical current, light, and heat.Comment: 47 pages, 41 figure
Reconfigurable Boolean Logic using Magnetic Single-Electron Transistors
We propose a novel hybrid single-electron device for reprogrammable low-power
logic operations, the magnetic single-electron transistor (MSET). The device
consists of an aluminium single-electron transistors with a GaMnAs magnetic
back-gate. Changing between different logic gate functions is realized by
reorienting the magnetic moments of the magnetic layer which induce a voltage
shift on the Coulomb blockade oscillations of the MSET. We show that we can
arbitrarily reprogram the function of the device from an n-type SET for
in-plane magnetization of the GaMnAs layer to p-type SET for out-of-plane
magnetization orientation. Moreover, we demonstrate a set of reprogrammable
Boolean gates and its logical complement at the single device level. Finally,
we propose two sets of reconfigurable binary gates using combinations of two
MSETs in a pull-down network
Detectability of atmospheric features of Earth-like planets in the habitable zone around M dwarfs
We investigate the detectability of atmospheric spectral features of
Earth-like planets in the habitable zone (HZ) around M dwarfs with the future
James Webb Space Telescope (JWST). We use a coupled 1D climate-chemistry-model
to simulate the influence of a range of observed and modelled M-dwarf spectra
on Earth-like planets. The simulated atmospheres served as input for the
calculation of the transmission spectra of the hypothetical planets, using a
line-by-line spectral radiative transfer model. To investigate the
spectroscopic detectability of absorption bands with JWST we further developed
a signal-to-noise ratio (S/N) model and applied it to our transmission spectra.
High abundances of CH and HO in the atmosphere of Earth-like planets
around mid to late M dwarfs increase the detectability of the corresponding
spectral features compared to early M-dwarf planets. Increased temperatures in
the middle atmosphere of mid- to late-type M-dwarf planets expand the
atmosphere and further increase the detectability of absorption bands. To
detect CH, HO, and CO in the atmosphere of an Earth-like planet
around a mid to late M dwarf observing only one transit with JWST could be
enough up to a distance of 4 pc and less than ten transits up to a distance of
10 pc. As a consequence of saturation limits of JWST and less pronounced
absorption bands, the detection of spectral features of hypothetical Earth-like
planets around most early M dwarfs would require more than ten transits. We
identify 276 existing M dwarfs (including GJ 1132, TRAPPIST-1, GJ 1214, and LHS
1140) around which atmospheric absorption features of hypothetical Earth-like
planets could be detected by co-adding just a few transits. We show that using
transmission spectroscopy, JWST could provide enough precision to be able to
partly characterise the atmosphere of Earth-like TESS planets around mid to
late M dwarfs.Comment: 18 pages, 10 figure
Franck-Condon Physics in A Single Trapped Ion
We propose how to explore the Franck-Condon (FC) physics via a single ion
confined in a spin-dependent potential, formed by the combination of a Paul
trap and a magnetic field gradient. The correlation between electronic and
vibrational degrees of freedom, called as electron-vibron coupling, is induced
by a nonzero gradient. For a sufficiently strong electron-vibron coupling, the
FC blockade of low-lying vibronic transitions takes place. We analyze the
feasibility of observing the FC physics in a single trapped ion, and
demonstrate various potential applications of the ionic FC physics in quantum
state engineering and quantum information processing.Comment: 7 pages, 5 figure
Tunneling anisotropic magnetoresistance in multilayer-(Co/Pt)/AlOx/Pt structures
We report observations of tunneling anisotropic magnetoresitance (TAMR) in
vertical tunnel devices with a ferromagnetic multilayer-(Co/Pt) electrode and a
non-magnetic Pt counter-electrode separated by an AlOx barrier. In stacks with
the ferromagnetic electrode terminated by a Co film the TAMR magnitude
saturates at 0.15% beyond which it shows only weak dependence on the magnetic
field strength, bias voltage, and temperature. For ferromagnetic electrodes
terminated by two monolayers of Pt we observe order(s) of magnitude enhancement
of the TAMR and a strong dependence on field, temperature and bias. Discussion
of experiments is based on relativistic ab initio calculations of magnetization
orientation dependent densities of states of Co and Co/Pt model systems.Comment: 4 pages, 5 figures, to be published in Phys. Rev. Let
- …