18,683 research outputs found
Electronic properties of correlated metals in the vicinity of a charge order transition: optical spectroscopy of -(BEDT-TTF)Hg(SCN) ( = NH, Rb, Tl)
The infrared spectra of the quasi-two-dimensional organic conductors
-(BEDT-TTF)Hg(SCN) ( = NH, Rb, Tl) were measured in
the range from 50 to 7000 \cm down to low temperatures in order to explore the
influence of electronic correlations in quarter-filled metals. The
interpretation of electronic spectra was confirmed by measurements of pressure
dependant reflectance of -(BEDT-TTF)KHg(SCN) at T=300 K. The
signatures of charge order fluctuations become more pronounced when going from
the NH salt to Rb and further to Tl compounds. On reducing the temperature,
the metallic character of the optical response in the NH and Rb salts
increases, and the effective mass diminishes. For the Tl compound, clear
signatures of charge order are found albeit the metallic properties still
dominate. From the temperature dependence of the electronic scattering rate the
crossover temperature is estimated below which the coherent charge-carriers
response sets in. The observations are in excellent agreement with recent
theoretical predictions for a quarter-filled metallic system close to charge
order
The D0 same-charge dimuon asymmetry and possibile new CP violation sources in the system
Recently, the D0 collaboration reported a large CP violation in the same-sign
dimuon charge asymmetry which has the deviation from the value
estimated in the Standard Model. In this paper, several new physics models are
considered: the MSSM, two Higgs doublet model, the recent dodeca model, and a
new model. Generally, it is hard to achieve such a large CP violation
consistently with other experimental constraints. We find that a scheme with
extra non-anomalous U(1) gauge symmetry is barely consistent. In general,
the extra gauge boson induces the flavor changing neutral current
interactions at tree level, which is the basic reason allowing a large new
physics CP violation. To preserve the U(1) symmetry at high energy,
SU(2) singlet exotic heavy quarks of mass above 1 TeV and the Standard
Model gauge singlet scalars are introduced.Comment: 12 pages, 13 figure
Anisotropic sub-Doppler laser cooling in dysprosium magneto-optical traps
Magneto-optical traps (MOTs) of Er and Dy have recently been shown to exhibit
population-wide sub-Doppler cooling due to their near degeneracy of excited and
ground state Lande g factors. We discuss here an additional, unusual intra-MOT
sub-Doppler cooling mechanism that appears when the total Dy MOT cooling laser
intensity and magnetic quadrupole gradient increase beyond critical values.
Specifically, anisotropically sub-Doppler-cooled cores appear, and their
orientation with respect to the quadrupole axis flips at a critical ratio of
the MOT laser intensity along the quadrupole axis versus that in the plane of
symmetry. This phenomenon can be traced to a loss of the velocity-selective
resonance at zero velocity in the cooling force along directions in which the
atomic polarization is oriented by the quadrupole field. We present data
characterizing this anisotropic laser cooling phenomenon and discuss a
qualitative model for its origin based on the extraordinarily large Dy magnetic
moment and Dy's near degenerate g factors.Comment: 4 pages, 5 figure
Automated verification of shape, size and bag properties.
In recent years, separation logic has emerged as a contender for formal reasoning of heap-manipulating imperative programs. Recent works have focused on specialised provers that are mostly based on fixed sets of predicates. To improve expressivity, we have proposed a prover that can automatically handle user-defined predicates. These shape predicates allow programmers to describe a wide range of data structures with their associated size properties. In the current work, we shall enhance this prover by providing support for a new type of constraints, namely bag (multi-set) constraints. With this extension, we can capture the reachable nodes (or values) inside a heap predicate as a bag constraint. Consequently, we are able to prove properties about the actual values stored inside a data structure
Metallic characteristics in superlattices composed of insulators, NdMnO3/SrMnO3/LaMnO3
We report on the electronic properties of superlattices composed of three
different antiferromagnetic insulators, NdMnO3/SrMnO3/LaMnO3 grown on SrTiO3
substrates. Photoemission spectra obtained by tuning the x-ray energy at the Mn
2p -> 3d edge show a Fermi cut-off, indicating metallic behavior mainly
originating from Mn e_g electrons. Furthermore, the density of states near the
Fermi energy and the magnetization obey a similar temperature dependence,
suggesting a correlation between the spin and charge degrees of freedom at the
interfaces of these oxides
Charge ordering in theta-(BEDT-TTF)_2 X materials
We investigate theoretically charge ordered states on the anisotropic
triangular lattice characteristic of the theta-(BEDT-TTF)_2 X materials. Using
exact diagonalization studies, we establish that the charge order (CO) pattern
corresponds to a ``horizontal'' stripe structure, with ...1100... CO along the
two directions with larger electron hopping (p-directions), and ...1010... CO
along the third direction (c-direction). The CO is accompanied by co-operative
bond dimerizations along all three directions in the highest spin state. In the
lowest spin state bonds along the p-directions are tetramerized. Our theory
explains the occurence of a charge-induced high temperature transition as well
as a spin gap transition at lower temperature.Comment: 4 pages, 4 eps figures, uses jpsj2.cl
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