22,613 research outputs found
Superconductivity-induced Phonon Renormalization on NaFeCoAs
We report a study of the lattice dynamics in superconducting NaFeAs (Tc = 8
K) and doped NaFe0.97Co0.03As (Tc = 20 K) using Raman light scattering. Five of
the six phonon modes expected from group theory are observed. In contrast with
results obtained on iso-structural and iso-electronic LiFeAs, anomalous
broadening of Eg(As) and A1g(Na) modes upon cooling is observed in both
samples. In addition, in the Co-doped sample, a superconductivity-induced
renormalization of the frequency and linewidth of the B1g(Fe) vibration is
observed. This renormalization can not be understood within a single band and
simple multi-band approaches. A theoretical model that includes the effects of
SDW correlations along with sign-changing s-wave pairing state and interband
scattering has been developed to explain the observed behavior of the B1g(Fe)
mode.Comment: 10 pages; 6 figure
The Gluon Spin in the Chiral Bag Model
We study the gluon polarization contribution at the quark model
renormalization scale to the proton spin, , in the chiral bag model. It
is evaluated by taking the expectation value of the forward matrix element of a
local gluon operator in the axial gauge . It is shown that the confining
boundary condition for the color electric field plays an important role. When a
solution satisfying the boundary condition for the color electric field, which
is not the conventionally used but which we favor, is used, the has a
positive value for {\it all} bag radii and its magnitude is comparable to the
quark spin polarization. This results in a significant reduction in the
relative fraction of the proton spin carried by the quark spin, which is
consistent with the small flavor singlet axial current measured in the EMC
experiments.Comment: Corrections to figure
Scheme for remote implementation of partially unknown quantum operation of two qubits in cavity QED
By constructing the recovery operations of the protocol of remote
implementation of partially unknown quantum operation of two qubits [An Min
Wang: PRA, \textbf{74}, 032317(2006)], we present a scheme to implement it in
cavity QED. Long-lived Rydberg atoms are used as qubits, and the interaction
between the atoms and the field of cavity is a nonresonant one. Finally, we
analyze the experimental feasibility of this scheme.Comment: 7 pages, 2 figure
Raman Scattering Study of the Lattice Dynamics of Superconducting LiFeAs
We report an investigation of the lattice dynamical properties of LiFeAs
using inelastic light scattering. Five out of the six expected phonon modes are
observed. The temperature evolution of their frequencies and linewidths is in
good agreement with an anharmonic-decay model. We find no evidence for
substantial electron-phonon coupling, and no superconductivity-induced phonon
anomalies.Comment: 5 pages, 3 figures, 1 tabl
Density functional calculations of the electronic structure and magnetic properties of the hydrocarbon K3picene superconductor near the metal-insulator transition
We have investigated the electronic structures and magnetic properties of of
K3picene, which is a first hydrocarbon superconductor with high transition
temperature T_c=18K. We have shown that the metal-insulator transition (MIT) is
driven in K3picene by 5% volume enhancement with a formation of local magnetic
moment. Active bands for superconductivity near the Fermi level E_F are found
to have hybridized character of LUMO and LUMO+1 picene molecular orbitals.
Fermi surfaces of K3picene manifest neither prominent nesting feature nor
marked two-dimensional behavior. By estimating the ratio of the Coulomb
interaction U and the band width W of the active bands near E_F, U/W, we have
demonstrated that K3picene is located in the vicinity of the Mott transition.Comment: 5 pages, 5 figure
Entangling two superconducting LC coherent modes via a superconducting flux qubit
Based on a pure solid-state device consisting of two superconducting LC
circuits coupled to a superconducting flux qubit, we propose in this paper that
the maximally entangled coherent states of the two LC modes can be generated
for arbitrary coherent states through flux qubit controls.Comment: 5 pages, 2 figure
- …