1,948 research outputs found
Noncontact modulation calorimetry of metallic liquids in low Earth orbit
Noncontact modulation calorimetry using electromagnetic heating and radiative heat loss under ultrahigh-vacuum conditions has been applied to levitated solid, liquid, and metastable liquid samples. This experiment requires a reduced gravity environment over an extended period of time and allows the measurement of several thermophysical properties, such as the enthalpy of fusion and crystallization, specific heat, total hemispherical emissivity, and effective thermal conductivity with high precision as a function of temperature. From the results on eutectic glass forming Zr-based alloys thermodynamic functions are obtained which describe the glass-forming ability of these alloys
Thermodynamics of Cu47Ti34Zr11Ni8, Zr52.5Cu17.9Ni14.6Al10Ti5 and Zr57Cu15.4Ni12.6Al10Nb5 bulk metallic glass forming alloys
The differences in the thermodynamic functions between the liquid and the crystalline states of three bulk metallic glass forming alloys, Cu47Ti34Zr11Ni8, Zr52.5Cu17.9Ni14.6Al10Ti5, and Zr57Cu15.4Ni12.6Al10Nb5, were calculated. The heat capacity was measured in the crystalline solid, the amorphous solid, the supercooled liquid, and the equilibrium liquid. Using these heat capacity data and the heats of fusion of the alloys, the differences in the thermodynamic functions between the liquid and the crystalline states were determined. The Gibbs free energy difference between the liquid and the crystalline states gives a qualitative measure of the glass forming ability of these alloys. Using the derived entropy difference, the Kauzmann temperatures for these alloys were determined
Generation of entangled photons by trapped ions in microcavities under a magnetic field gradient
We propose a potential scheme to generate entangled photons by manipulating
trapped ions embedded in two-mode microcavities, respectively, assisted by a
magnetic field gradient. By means of the spin-spin coupling due to the magnetic
field gradient and the Coulomb repulsion between the ions, we show how to
efficiently generate entangled photons by detecting the internal states of the
trapped ions. We emphasize that our scheme is advantageous to create complete
sets of entangled multi-photon states. The requirement and the experimental
feasibility of our proposal are discussed in detail.Comment: 2 Tables, 2 Figures, To appear in Phys. Rev.
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
Consistently Simulating a Wide Range of Atmospheric Scenarios for K2-18b with a Flexible Radiative Transfer Module
The atmospheres of small, potentially rocky exoplanets are expected to cover
a diverse range in composition and mass. Studying such objects therefore
requires flexible and wide-ranging modeling capabilities. We present in this
work the essential development steps that lead to our flexible radiative
transfer module, REDFOX, and validate REDFOX for the Solar system planets
Earth, Venus and Mars, as well as for steam atmospheres. REDFOX is a
k-distribution model using the correlated-k approach with random overlap method
for the calculation of opacities used in the -two-stream approximation
for radiative transfer. Opacity contributions from Rayleigh scattering, UV /
visible cross sections and continua can be added selectively. With the improved
capabilities of our new model, we calculate various atmospheric scenarios for
K2-18b, a super-Earth / sub-Neptune with 8 M orbiting in the
temperate zone around an M-star, with recently observed HO spectral
features in the infrared. We model Earth-like, Venus-like, as well as H-He
primary atmospheres of different Solar metallicity and show resulting climates
and spectral characteristics, compared to observed data. Our results suggest
that K2-18b has an H-He atmosphere with limited amounts of HO and
CH. Results do not support the possibility of K2-18b having a water
reservoir directly exposed to the atmosphere, which would reduce atmospheric
scale heights, hence too the amplitudes of spectral features inconsistent with
the observations. We also performed tests for H-He atmospheres up to 50
times Solar metallicity, all compatible with the observations.Comment: 28 pages, 13 figures, accepted for publication in Ap
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
Unconditional Bell-type state generation for spatially separate trapped ions
We propose a scheme for generation of maximally entangled states involving
internal electronic degrees of freedom of two distant trapped ions, each of
them located in a cavity. This is achieved by using a single flying atom to
distribute entanglement. For certain specific interaction times, the proposed
scheme leads to the non-probabilistic generation of a perfect Bell-type state.
At the end of the protocol, the flying atom completely disentangles from the
rest of the system, leaving both ions in a Bell-type state. Moreover, the
scheme is insensitive to the cavity field state and cavity losses. We also
address the situation in which dephasing and dissipation must be taken into
account for the flying atom on its way from one cavity to the other, and
discuss the applicability of the resulting noisy channel for performing quantum
teleportation.Comment: 5 pages, 1 figure, detailed comments on the practical implementation
of the scheme is added to replaced version, minor typos fixed, added
references with comment
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
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