3,288 research outputs found
Theory for superconductivity in (Tl,K)FeSe as a doped Mott insulator
Possible superconductivity in recently discovered (Tl,K)FeSe
compounds is studied from the viewpoint of doped Mott insulator. The Mott
insulating phase is examined to be preferred in the parent compound at
due to the presence of Fe vacancies. Partial filling of vacancies at the
Fe-sites introduces electron carriers and leads to electron doped
superconductivity. By using a two-orbital Hubbard model in the strong coupling
limit, we find that the s-wave pairing is more favorable at small Hund's
coupling, and d wave pairing is more favorable at large Hund's
coupling.Comment: 4+ pages, 3 figures, to appear in EP
Centrality dependence of spectra for identified hadrons in Au+Au and Cu+Cu collisions at GeV
The centrality dependence of transverse momentum spectra for identified
hadrons at midrapidity in Au+Au collisions at GeV is
systematically studied in a quark combination model. The
spectra of , , and in
different centrality bins and the nuclear modification factors () for
these hadrons are calculated. The centrality dependence of the average
collective transverse velocity for the hot and dense quark matter
is obtained in Au+Au collisions, and it is applied to a relative smaller Cu+Cu
collision system. The centrality dependence of spectra and
the for , and in Cu+Cu collisions at
GeV are well described. The results show that is only a function of the number of participants and it is
independent of the collision system.Comment: 7 pages, 6 figure
Avoided Quantum Criticality and Magnetoelastic Coupling in BaFe<sub>2-</sub>xNi<sub>x</sub>As<sub>2</sub>
We study the structural and magnetic orders in electron-doped BaFe2-xNixAs2
by high-resolution synchrotron X-ray and neutron scatterings. Upon Ni-doping x,
the nearly simultaneous tetragonal-to-orthorhombic structural T_s and
antiferromagnetic (T_N) phase transitions in BaFe2As2 are gradually suppressed
and separated, resulting in T_s>T_N with increasing x as was previously
observed. However, the temperature separation between T_s and T_N decreases
with increasing x for x> 0.065 K
above the superconducting dome around . Our results imply an
avoided quantum critical point, which is expected to strongly influence the
properties of both the normal and superconducting states.Comment: 7 pages; 5 figure
Quantum phase transition and destruction of Kondo effect in pressurized SmB6
SmB6 is a promising candidate material that promises to elucidate the
connection between strong correlations and topological electronic states, which
is a major challenge in condensed matter physics. The electron correlations are
responsible for the development of multiple gaps in SmB6, whose elucidation is
sorely needed. Here we do so by studying the evolutions of the gaps and other
corresponding behaviors under pressure. Our measurements of the valence, Hall
effect and electrical resistivity clearly identify the gap which is associated
with the bulk Kondo hybridization and, moreover, uncover a pressure-induced
quantum phase transition from the putative topological Kondo insulating state
to a Fermi-liquid state at ~4 GPa. We provide the evidences for the transition
by a jump of inverse Hall coefficient, a diverging tendency of the
electron-electron scattering coefficient and, thereby, a destruction of the
Kondo entanglement in the ground state. These effects take place in a
mixed-valence background. Our results raise the new prospect for studying
topological electronic states in quantum critical materials settings.Comment: 18 pages and 3 figure
PTPα regulates integrin-stimulated FAK autophosphorylation and cytoskeletal rearrangement in cell spreading and migration
We investigated the molecular and cellular actions of receptor protein tyrosine phosphatase (PTP) α in integrin signaling using immortalized fibroblasts derived from wild-type and PTPα-deficient mouse embryos. Defects in PTPα−/− migration in a wound healing assay were associated with altered cell shape and focal adhesion kinase (FAK) phosphorylation. The reduced haptotaxis to fibronectin (FN) of PTPα−/− cells was increased by expression of active (but not inactive) PTPα. Integrin-mediated formation of src–FAK and fyn–FAK complexes was reduced or abolished in PTPα−/− cells on FN, concomitant with markedly reduced phosphorylation of FAK at Tyr397. Reintroduction of active (but not inactive) PTPα restored FAK Tyr-397 phosphorylation. FN-induced cytoskeletal rearrangement was retarded in PTPα−/− cells, with delayed filamentous actin stress fiber assembly and focal adhesion formation. This mimicked the effects of treating wild-type fibroblasts with the src family protein tyrosine kinase (Src-PTK) inhibitor PP2. These results, together with the reduced src/fyn tyrosine kinase activity in PTPα−/− fibroblasts (Ponniah et al., 1999; Su et al., 1999), suggest that PTPα functions in integrin signaling and cell migration as an Src-PTK activator. Our paper establishes that PTPα is required for early integrin-proximal events, acting upstream of FAK to affect the timely and efficient phosphorylation of FAK Tyr-397
Near-transform-limited single photons from an efficient solid-state quantum emitter
This work was supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences, the National Fundamental Research Program, and the State of Bavaria.By pulsed s-shell resonant excitation of a single quantum dot-micropillar system, we generate long streams of 1000 near-transform-limited single photons with high mutual indistinguishability. The Hong-Ou-Mandel interference of two photons is measured as a function of their emission time separation varying from 13 ns to 14.7 μs, where the visibility slightly drops from 95.9(2)% to a plateau of 92.1(5)% through a slow dephasing process occurring at a time scale of 0.7 μs. A temporal and spectral analysis reveals the pulsed resonance fluorescence single photons are close to the transform limit, which are readily useful for multiphoton entanglement and interferometry experiments.Publisher PDFPeer reviewe
Rare germline variants in DNA repair genes and the angiogenesis pathway predispose prostate cancer patients to develop metastatic disease
Background
Prostate cancer (PrCa) demonstrates a heterogeneous clinical presentation ranging from largely indolent to lethal. We sought to identify a signature of rare inherited variants that distinguishes between these two extreme phenotypes.
Methods
We sequenced germline whole exomes from 139 aggressive (metastatic, age of diagnosis < 60) and 141 non-aggressive (low clinical grade, age of diagnosis ≥60) PrCa cases. We conducted rare variant association analyses at gene and gene set levels using SKAT and Bayesian risk index techniques. GO term enrichment analysis was performed for genes with the highest differential burden of rare disruptive variants.
Results
Protein truncating variants (PTVs) in specific DNA repair genes were significantly overrepresented among patients with the aggressive phenotype, with BRCA2, ATM and NBN the most frequently mutated genes. Differential burden of rare variants was identified between metastatic and non-aggressive cases for several genes implicated in angiogenesis, conferring both deleterious and protective effects.
Conclusions
Inherited PTVs in several DNA repair genes distinguish aggressive from non-aggressive PrCa cases. Furthermore, inherited variants in genes with roles in angiogenesis may be potential predictors for risk of metastases. If validated in a larger dataset, these findings have potential for future clinical application
Generalized Toric Codes Coupled to Thermal Baths
We have studied the dynamics of a generalized toric code based on qudits at
finite temperature by finding the master equation coupling the code's degrees
of freedom to a thermal bath. As a consequence, we find that for qutrits new
types of anyons and thermal processes appear that are forbidden for qubits.
These include creation, annihilation and diffusion throughout the system code.
It is possible to solve the master equation in a short-time regime and find
expressions for the decay rates as a function of the dimension of the
qudits. Although we provide an explicit proof that the system relax to the
Gibbs state for arbitrary qudits, we also prove that above a certain crossing
temperature, qutrits initial decay rate is smaller than the original case for
qubits. Surprisingly this behavior only happens with qutrits and not with other
qudits with .Comment: Revtex4 file, color figures. New Journal of Physics' versio
Constraints from Solar and Reactor Neutrinos on Unparticle Long-Range Forces
We have investigated the impact of long-range forces induced by unparticle
operators of scalar, vector and tensor nature coupled to fermions in the
interpretation of solar neutrinos and KamLAND data. If the unparticle couplings
to the neutrinos are mildly non-universal, such long-range forces will not
factorize out in the neutrino flavour evolution. As a consequence large
deviations from the observed standard matter-induced oscillation pattern for
solar neutrinos would be generated. In this case, severe limits can be set on
the infrared fix point scale, Lambda_u, and the new physics scale, M, as a
function of the ultraviolet (d_UV) and anomalous (d) dimension of the
unparticle operator. For a scalar unparticle, for instance, assuming the
non-universality of the lepton couplings to unparticles to be of the order of a
few per mil we find that, for d_UV=3 and d=1.1, M is constrained to be M >
O(10^9) TeV (M > O(10^10) TeV) if Lambda_u= 1 TeV (10 TeV). For given values of
Lambda_u and d, the corresponding bounds on M for vector [tensor] unparticles
are approximately 100 [3/Sqrt(Lambda_u/TeV)] times those for the scalar case.
Conversely, these results can be translated into severe constraints on
universality violation of the fermion couplings to unparticle operators with
scales which can be accessible at future colliders.Comment: 13 pages, 3 figures. Minor changes due to precision in numerical
factors and correction in figure labels. References added. Conclusions remain
unchange
Commensurate dynamic magnetic correlations in La2(Cu,Li)O4
When sufficient numbers of holes are introduced into the two-dimensional CuO2
square lattice, dynamic magnetic correlations become incommensurate with
underlying lattice in all previously investigated La_{2-x}A_xCu_{1-z}B_zO_{4+y}
(A=Sr or Nd, B=Zn) including high T_C superconductors and insulators, and in
bilayered superconducting YBa_2Cu_3O_{6.6} and Bi_2Sr_2CaCu_2O_8. Magnetic
correlations also become incommensurate in structurally related La_2NiO_4 when
doped with Sr or O. We report an exception to this so-far well established
experimental "rule" in La_2Cu_{1-z}Li_{z}O_4 in which magnetic correlations
remain commensurate.Comment: 4 pages, 3 figures, revised version as for publicatio
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