2,149 research outputs found
New Ideas on SUSY Searches at Future Linear Colliders
Several results obtained within the SUSY group of the ECFA/DESY linear
collider study are presented: (i) a possibility to determine tan beta and the
trilinear couplings A_f via polarisation in sfermion decays, (ii) the impact of
complex MSSM parameters on the third generation sfermion decays, (iii)
determination of CP violation in the complex MSSM via T-odd asymmetries in
neutralino production and decay, and (iv) an analysis of the chargino and
neutralino mass parameters at one-loop level.Comment: 3 pages, LaTeX, 5 eps figures; talk presented by S. Hesselbach at the
International Europhysics Conference on High Energy Physics (HEP 2003), 17-23
July 2003, Aachen, German
Supersolid phases of dipolar bosons in optical lattices with a staggered flux
We present the theoretical mean-field zero-temperature phase diagram of a
Bose-Einstein condensate (BEC) with dipolar interactions loaded into an optical
lattice with a staggered flux. Apart from uniform superfluid, checkerboard
supersolid and striped supersolid phases, we identify several supersolid phases
with staggered vortices, which can be seen as combinations of supersolid phases
found in earlier work on dipolar BECs and a staggered-vortex phase found for
bosons in optical lattices with staggered flux. By allowing for different
phases and densities on each of the four sites of the elementary plaquette,
more complex phase patterns are found.Comment: 11 pages; added references, minor changes in tex
Universal Decoherence in Solids
Symmetry implications for the decoherence of quantum oscillations of a
two-state system in a solid are studied. When the oscillation frequency is
small compared to the Debye frequency, the universal lower bound on the
decoherence due to the atomic environment is derived in terms of the
macroscopic parameters of the solid, with no unknown interaction constants.Comment: 4 pages, no figure
Impact of CP phases on SUSY particle production and decays
We report on the results of a phenomenological study of top squarks
(stop_{1,2}) and bottom squarks (sbottom_{1,2}) in the Minimal Supersymmetric
Standard Model (MSSM) with complex parameters A_t, A_b, mu and M_1. In
particular we focus on the CP phase dependence of the branching ratios of
stop_{1,2} and sbottom_{1,2} decays. We find that the effect of the phases on
the stop_{1,2} and sbottom_{1,2} decays can be quite significant in a large
region of the MSSM parameter space. We also study a CP asymmetry in sfermion
decays.Comment: 10 pages, 8 eps figures, LaTeX, uses JHEP3.cls; talk given at the
International Workshop on Astroparticle and High Energy Physics (AHEP),
Valencia, Spain, 14-18 Oct. 200
Three-terminal thermoelectric transport through a molecule placed on an Aharonov-Bohm ring
The thermoelectric transport through a ring threaded by an Aharonov-Bohm
flux, with a molecular bridge on one of its arms, is analyzed. The transport
electrons also interact with the vibrational excitations of that molecule. This
nano-system is connected to three terminals: two are electronic reservoirs,
which supply the transport electrons, and the third is the phonon bath which
thermalizes the molecular vibrations. Expressions for the transport
coefficients, relating all charge and heat currents to the temperature and
chemical potential differences between the terminals, are derived to second
order in the electron-vibration coupling. At linear response, all these
coefficients obey the full Onsager-Casimir relations. When the phonon bath is
held at a temperature different from those of the electronic reservoirs, a heat
current exchanged between the molecular vibrations and the transport electrons
can be converted into electric and/or heat electronic currents. The related
transport coefficients, which exist only due to the electron-vibration
coupling, change sign under the interchange between the electronic terminals
and the sign change of the magnetic flux. It is also demonstrated that the
Aharonov-Bohm flux can enhance this type of conversion.Comment: Added clearer kists of the new result
Current-Driven Magnetic Excitations in Permalloy-Based Multilayer Nanopillars
We study current-driven magnetization switching in nanofabricated
Ni84Fe16/Cu/Ni84Fe16 trilayers at 295 K and 4.2 K. The shape of the hysteretic
switching diagram at low magnetic field changes from 295 K to 4.2 K. The
reversible behavior at higher field involves two phenomena, a threshold current
for magnetic excitations closely correlated with the switching current, and a
peak in differential resistance characterized by telegraph noise, with average
period that decreases exponentially with current and shifts with temperature.
We interpret both static and dynamic results at 295 K and 4.2 K in terms of
thermal activation over a potential barrier, with a current dependent effective
magnetic temperature.Comment: 4 pages, 4 Figure
Tuning of magnetic and electronic states by control of oxygen content in lanthanum strontium cobaltites
We report on the magnetic, resistive, and structural studies of perovskite
LaSrCoO. By using the relation of synthesis
temperature and oxygen partial pressure to oxygen stoichiometry obtained from
thermogravimetric analysis, we have synthesized a series of samples with
precisely controlled . These samples show three structural
phases at , , , and two-phase
behavior for other oxygen contents. The stoichiometric material with
is a cubic ferromagnetic metal with the Curie temperature K. The increase of to 0.15 is followed by a linear decrease of
to 160 K and a metal-insulator transition near the
boundary of the cubic structure range. Further increase of results in
formation of a tetragonal phase for
and a brownmillerite phase for . At low
temperatures, these are weak ferromagnetic insulators (canted antiferromagnets)
with magnetic transitions at and 120 K, respectively. At
higher temperatures, the phase is -type
antiferromagnetic between 230 K and 360 K. Low temperature magnetic
properties of this system for can be described in terms of a
mixture of Co ions in the low-spin state and Co ions in the
intermediate-spin state and a possible spin transition of Co to the
intermediate-spin state above . For , there appears to
be a combination of Co and Co ions, both in the high-spin state
with dominating antiferromagnetic interactions.Comment: RevTeX, 9 pages, 7 figures, to be published in Physical Review
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