563 research outputs found
Magnetic Phase Diagram of the Hole-doped CaNaCuOCl Cuprate Superconductor
We report on the magnetic phase diagram of a hole-doped cuprate
CaNaCuOCl, which is free from buckling of CuO
planes, determined by muon spin rotation and relaxation. It is characterized by
a quasi-static spin glass-like phase over a range of sodium concentration
(), which is held between long range antiferromagnetic
(AF) phase () and superconducting phase where the system is
non-magnetic for . The obtained phase diagram qualitatively agrees
well with that commonly found for hole-doped high-\tc cuprates, strongly
suggesting that the incomplete suppression of the AF order for is an
essential feature of the hole-doped cuprates.Comment: 5 pages, submitted to Phys. Rev. Let
Visualizing the emergence of the pseudogap state and the evolution to superconductivity in a lightly hole-doped Mott insulator
Superconductivity emerges from the cuprate antiferromagnetic Mott state with
hole doping. The resulting electronic structure is not understood, although
changes in the state of oxygen atoms appear paramount. Hole doping first
destroys the Mott state yielding a weak insulator where electrons localize only
at low temperatures without a full energy gap. At higher doping, the
'pseudogap', a weakly conducting state with an anisotropic energy gap and
intra-unit-cell breaking of 90\degree-rotational (C4v) symmetry appears.
However, a direct visualization of the emergence of these phenomena with
increasing hole density has never been achieved. Here we report atomic-scale
imaging of electronic structure evolution from the weak-insulator through the
emergence of the pseudogap to the superconducting state in Ca2-xNaxCuO2Cl2. The
spectral signature of the pseudogap emerges at lowest doping from a weakly
insulating but C4v-symmetric matrix exhibiting a distinct spectral shape. At
slightly higher hole-density, nanoscale regions exhibiting pseudogap spectra
and 180\degree-rotational (C2v) symmetry form unidirectional clusters within
the C4v-symmetric matrix. Thus, hole-doping proceeds by the appearance of
nanoscale clusters of localized holes within which the broken-symmetry
pseudogap state is stabilized. A fundamentally two-component electronic
structure11 then exists in Ca2-xNaxCuO2Cl2 until the C2v-symmetric clusters
touch at higher doping, and the long-range superconductivity appears.Comment: See the Nature Physics website for the published version available at
http://dx.doi.org/10.1038/Nphys232
Free boundary problem for quasilinear parabolic equation with fixed angle of contact to a boundary
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