19,675 research outputs found
Detecting the orbital character of the spin fluctuation in the Iron-based superconductors with the resonant inelastic X-ray scattering spectroscopy
The orbital distribution of the spin fluctuation in the iron-based
superconductors(IBSs) is the key information needed to understand the
magnetism, superconductivity and electronic nematicity in these multi-orbital
systems. In this work, we propose that the resonant inelastic X-ray
scattering(RIXS) technique can be used to probe selectively the spin
fluctuation on different Fe orbitals. In particular, the spin fluctuation
on the three orbitals, namely, the , and the
orbital, can be selectively probed in the
scattering geometry by aligning the direction of the outgoing photon in the
, and direction. Such orbital-resolved information on the spin
fluctuation is invaluable for the study of the orbital-selective physics in the
IBSs and can greatly advance our understanding on the relation between orbital
ordering and spin nematicity in the IBSs and the orbital-selective pairing
mechanism in these multi-orbital systems.Comment: 6 pages with new and more informative figures, the explicit form of
the RIXS matrix element is provided, and the discussion part has been
rewritte
Vanishing pseudogap around in an electron-doped high- superconductor: a simple picture
Recent ARPES measurement on electron-doped cuprate
finds
that the pseudogap along the boundary of the antiferromagnetic Brillouin
zone(AFBZ) exhibits dramatic momentum dependence. In particular, the pseudogap
vanishes in a finite region around the anti-nodal point, in which a single
broadened peak emerges at the un-renormalized quasiparticle energy. Such an
observation is argued to be inconsistent with the antiferromagnetic(AFM)
band-folding picture, which predicts a constant pseudogap along the AFBZ
boundary. On the other hand, it is claimed that the experimental results are
consistent with the prediction of the cluster dynamical mean field
theory(CDMFT) simulation on the Hubbard model, in which the pseudogap is
interpreted as a s-wave splitting between the Hubbard bands and the in-gap
states. Here we show that the observed momentum dependence of the pseudogap is
indeed consistent with AFM band-folding picture, provided that we assume the
existence of a strongly momentum dependent quasiparticle scattering rate. More
specifically, we show that the quasiparticle scattering rate acts to reduce the
spectral gap induced by AFM band-folding effect. The new quasiparticle poles
corresponding to the AF-split bands can even be totally eliminated when the
scattering rate exceeds the bare band folding gap, leaving the system with a
single pole at the un-renormalized quasiparticle energy. We predict that the
pseudogap should close in a square root fashion as we move toward
along the AFBZ boundary. Our results illustrates again that the quasiparticle
scattering rate can play a much more profound role than simply broadening the
quasiparticle peak in the quasiparticle dynamics of strongly correlated
electron systems.Comment: 5 pages, 2 figures, new references adde
Unparticle Physics Effects on D0-anti-D0 Mixing
The mixing of , and
provides a sensitive probe to explore new physics
beyond the Standard Model. The scale invariant unparticle physics recently
proposed by Georgi can induce flavor-changing neutral current and contribute to
the mixing at tree level. We investigate the unparticle effects on
and mixing. Especially, the newly observed
mixing sets the most stringent constraints on the coupling of
the unparticle to quarks.Comment: 9 pages, some errors corrected, published versio
Is a molecular state
Assuming the newly observed to be a molecular state of , we calculate the partial widths of and within the light front
model (LFM). is the channel by which was
observed, our calculation indicates that it is indeed one of the dominant modes
whose width can be in the range of a few MeV depending on the model parameters.
Similar to and , Voloshin suggested that there should be a
resonance at 4030 MeV which can be a molecular state of .
Then we go on calculating its decay rates to all the aforementioned final
states and as well the . It is found that if is a
molecular state of , the partial width of
is rather small, but the rate of
is even larger than . The
implications are discussed and it is indicated that with the luminosity of BES
and BELLE, the experiments may finally determine if is a molecular
state or a tetraquark.Comment: 17 pages, 6 figures, 3 table
Re-Study on the wave functions of states in LFQM and the radiative decays of
The Light-front quark model (LFQM) has been applied to calculate the
transition matrix elements of heavy hadron decays. However, it is noted that
using the traditional wave functions of the LFQM given in literature, the
theoretically determined decay constants of the obviously
contradict to the data. It implies that the wave functions must be modified.
Keeping the orthogonality among the states and fitting their decay
constants we obtain a series of the wave functions for . Based on
these wave functions and by analogy to the hydrogen atom, we suggest a modified
analytical form for the wave functions. By use of the modified
wave functions, the obtained decay constants are close to the experimental
data. Then we calculate the rates of radiative decays of . Our predictions are consistent with the experimental data on
decays within the theoretical and experimental
errors.Comment: 10 pages, 2 figures, 1 table. Typos corrected and more discussions
added. accepted for publication in Physical Review
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