4,493 research outputs found
Spin Inelastic Electron Tunneling Spectroscopy on Local Magnetic Moment Embedded in Josephson Junction
Recent experimental conductance measurements performed on paramagnetic
molecular adsorbates on a superconducting surface, using superconducting
scanning tunneling microscopy techniques, are theoretically investigated. For
low temperatures, we demonstrate that tunneling current assisted excitations of
the local magnetic moment cannot occur for voltage biases smaller than the
superconducting gap of the scanning tunneling microscope. The magnetic moment
is only excited for voltages corresponding to the sum of the superconducting
gap and the spin excitation energies. In excellent agreement with experiment,
we show that pumping into higher excitations give additional current signatures
by accumulation of density in the lower ones. Using external magnetic fields,
we Zeeman split possible degeneracy and thereby resolve all excitations
comprised in the magnetic moment.Comment: 6 pages, 4 figures, submitte
Electron Paramagnetic Resonance of Single Magnetic Moment on a Surface
We address electron spin resonance of single magnetic moments in a tunnel
junction using time-dependent electric fields and spin-polarized current. We
show that the tunneling current directly depends on the local magnetic moment
and that the frequency of the external electric field mixes with the
characteristic Larmor frequency of the local spin. The importance of the
spin-polarized current induced anisotropy fields acting on the local spin
moment is, moreover, demonstrated. Our proposed model thus explains the absence
of an electron spin resonance for a half integer spin, in contrast with the
strong signal observed for an integer spin.Comment: 6 pages, 2 figures, as publishe
Subroutine allows easy computation in extended precision arithmetic
Subroutine called NPREC allows relatively simple computation of very large numbers or very small fractions with extreme accuracy. This subroutine handles numbers that consist of 35 binary bits /1 word/ for the exponent and 70 bits /2 words/ for the fraction
Gamow Shell-Model Description of Weakly Bound and Unbound Nuclear States
Recently, the shell model in the complex k-plane (the so-called Gamow Shell
Model) has been formulated using a complex Berggren ensemble representing bound
single-particle states, single-particle resonances, and non-resonant continuum
states. In this framework, we shall discuss binding energies and energy spectra
of neutron-rich helium and lithium isotopes. The single-particle basis used is
that of the Hartree-Fock potential generated self-consistently by the
finite-range residual interaction.Comment: 13 pages, 2 figures, presented by N. Michel at the XXVII Symposium On
Nuclear Physics, Taxco, Guerrero, Mexico, January 5-8 200
Electrothermal feedback in superconducting nanowire single-photon detectors
We investigate the role of electrothermal feedback in the operation of
superconducting nanowire single-photon detectors (SNSPDs). It is found that the
desired mode of operation for SNSPDs is only achieved if this feedback is
unstable, which happens naturally through the slow electrical response
associated with their relatively large kinetic inductance. If this response is
sped up in an effort to increase the device count rate, the electrothermal
feedback becomes stable and results in an effect known as latching, where the
device is locked in a resistive state and can no longer detect photons. We
present a set of experiments which elucidate this effect, and a simple model
which quantitatively explains the results
Drell-Yan Production at NNLL'+NNLO Matched to Parton Showers
We present results for Drell-Yan production from the GENEVA Monte-Carlo
framework. We combine the fully-differential NNLO calculation with higher-order
resummation in the 0-jettiness resolution variable. The resulting parton-level
events are further combined with parton showering and hadronization provided by
PYTHIA8. The 0-jettiness resummation is carried out to NNLL', which
consistently incorporates all singular virtual and real NNLO corrections. It
thus provides a natural perturbative connection between the NNLO calculation
and the parton shower regime, including a systematic assessment of perturbative
uncertainties. In this way, inclusive observables are correct to NNLO, up to
small power corrections in the resolution cutoff. Furthermore, the perturbative
accuracy of 0-jet-like resummation variables is significantly improved beyond
the parton shower approximation. We provide comparisons with LHC measurements
of Drell-Yan production at 7 TeV from ATLAS, CMS, and LHCb. As already observed
in collisions, for resummation-sensitive observables, the agreement
with data is noticeably improved by using a lower value of .Comment: 26 pages, 20 figure
Timing performance of 30-nm-wide superconducting nanowire avalanche photodetectors
We investigated the timing jitter of superconducting nanowire avalanche
photodetectors (SNAPs, also referred to as cascade switching superconducting
single photon detectors) based on 30-nm-wide nanowires. At bias currents (IB)
near the switching current, SNAPs showed sub 35 ps FWHM Gaussian jitter similar
to standard 100 nm wide superconducting nanowire single-photon detectors. At
lower values of IB, the instrument response function (IRF) of the detectors
became wider, more asymmetric, and shifted to longer time delays. We could
reproduce the experimentally observed IRF time-shift in simulations based on an
electrothermal model, and explain the effect with a simple physical picture
Electric circuit networks equivalent to chaotic quantum billiards
We formulate two types of electric RLC resonance network equivalent to
quantum billiards. In the network of inductors grounded by capacitors squared
resonant frequencies are eigenvalues of the quantum billiard. In the network of
capacitors grounded by inductors squared resonant frequencies are given by
inverse eigen values of the billiard. In both cases local voltages play role of
the wave function of the quantum billiard. However as different from quantum
billiards there is a heat power because of resistance of the inductors. In the
equivalent chaotic billiards we derive the distribution of the heat power which
well describes numerical statistics.Comment: 9 pages, 7 figure
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