15,637 research outputs found
20 K superconductivity in heavily electron doped surface layer of FeSe bulk crystal
A superconducting transition temperature Tc as high as 100 K was recently
discovered in 1 monolayer (1ML) FeSe grown on SrTiO3 (STO). The discovery
immediately ignited efforts to identify the mechanism for the dramatically
enhanced Tc from its bulk value of 7 K. Currently, there are two main views on
the origin of the enhanced Tc; in the first view, the enhancement comes from an
interfacial effect while in the other it is from excess electrons with strong
correlation strength. The issue is controversial and there are evidences that
support each view. Finding the origin of the Tc enhancement could be the key to
achieving even higher Tc and to identifying the microscopic mechanism for the
superconductivity in iron-based materials. Here, we report the observation of
20 K superconductivity in the electron doped surface layer of FeSe. The
electronic state of the surface layer possesses all the key spectroscopic
aspects of the 1ML FeSe on STO. Without any interface effect, the surface layer
state is found to have a moderate Tc of 20 K with a smaller gap opening of 4
meV. Our results clearly show that excess electrons with strong correlation
strength alone cannot induce the maximum Tc, which in turn strongly suggests
need for an interfacial effect to reach the enhanced Tc found in 1ML FeSe/STO.Comment: 5 pages, 4 figure
Pairing Symmetry in the Anisotropic Fermi Superfluid under p-wave Feshbach Resonance
The anisotropic Fermi superfluid of ultra-cold Fermi atoms under the p-wave
Feshbach resonance is studied theoretically. The pairing symmetry of the ground
state is determined by the strength of the atom-atom magnetic dipole
interaction. It is for a strong dipole interaction; while it becomes , up to a rotation about z, for a weak one (Here < 1 is a
numerical coefficient). By changing the external magnetic field or the atomic
gas density, a phase transition between these two states can be driven. We
discuss how the pairing symmetry of the ground state can be determined in the
time-of-flight experiments.Comment: 12 pages, 7 figure
Hiding Single Photons With Spread Spectrum Technology
We describe a proof-of-principal experiment demonstrating the use of spread
spectrum technology at the single photon level. We show how single photons with
a prescribed temporal shape, in the presence of interfering noise, may be
hidden and recovered.Comment: 4 pages, 5 figures
- …