427 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
Crystal growth and magnetic structure of MnBi2Te4
Millimeter-sized MnBiTe single crystals are grown out of Bi-Te flux
and characterized by measuring magnetic and transport properties, scanning
tunneling microscope (STM) and spectroscopy (STS). The magnetic structure of
MnBiTe below T is determined by powder and single crystal neutron
diffraction measurements. Below T=24\,K, Mn moments order
ferromagnetically in the \textit{ab} plane but antiferromagnetically along the
crystallographic \textit{c} axis. The ordered moment is 4.04(13) /Mn
at 10\,K and aligned along the crystallographic \textit{c}-axis. The electrical
resistivity drops upon cooling across T or when going across the
metamagnetic transition in increasing fields below T. A critical scattering
effect was observed in the vicinity of T in the temperature dependence of
thermal conductivity. However, A linear temperature dependence was observed for
thermopower in the temperature range 2K-300K without any anomaly around T.
These indicate that the magnetic order in Mn-Te layer has negligible effect on
the electronic band structure, which makes possible the realization of proposed
topological properties in MnBiTe after fine tuning of the electronic
band structure
Liquid-like thermal conduction in a crystalline solid
A solid conducts heat through both transverse and longitudinal acoustic
phonons, but a liquid employs only longitudinal vibrations. Here, we report
that the crystalline solid AgCrSe2 has liquid-like thermal conduction. In this
compound, Ag atoms exhibit a dynamic duality that they are exclusively involved
in intense low-lying transverse acoustic phonons while they also undergo local
fluctuations inherent in an order-to-disorder transition occurring at 450 K. As
a consequence of this extreme disorder-phonon coupling, transverse acoustic
phonons become damped as approaching the transition temperature, above which
they are not defined anymore because their lifetime is shorter than the
relaxation time of local fluctuations. Nevertheless, the damped longitudinal
acoustic phonon survives for thermal transport. This microscopic insight might
reshape the fundamental idea on thermal transport properties of matter and
facilitates the optimization of thermoelectrics.Comment: four figures, supplemental informatio
Incommensurate Geometry of the Elastic Magnetic Peaks in Superconducting La1.88Sr0.12CuO4
We report magnetic neutron scattering measurements of incommensurate magnetic
order in a superconducting single crystal of La1.88Sr0.12CuO4. We find that the
incommensurate wavevectors which describe the static magnetism do not lie along
high-symmetry directions of the underlying CuO2 lattice. The positions of the
elastic magnetic peaks are consistent with those found in excess-oxygen doped
La2CuO4+y. This behavior differs from the precise magnetic order found in the
low temperature tetragonal La1.6-xNd0.4SrxCuO4 material for which stripes of
spin and charge have been observed. These observations have clear implications
for any stripe model proposed to describe the static magnetism in orthorhombic
La2CuO4-based superconductors.Comment: 4 pages, 3 eps figure
Mott physics, sign structure, ground state wavefunction, and high-Tc superconductivity
In this article I give a pedagogical illustration of why the essential
problem of high-Tc superconductivity in the cuprates is about how an
antiferromagnetically ordered state can be turned into a short-range state by
doping. I will start with half-filling where the antiferromagnetic ground state
is accurately described by the Liang-Doucot-Anderson (LDA) wavefunction. Here
the effect of the Fermi statistics becomes completely irrelevant due to the no
double occupancy constraint. Upon doping, the statistical signs reemerge,
albeit much reduced as compared to the original Fermi statistical signs. By
precisely incorporating this altered statistical sign structure at finite
doping, the LDA ground state can be recast into a short-range antiferromagnetic
state. Superconducting phase coherence arises after the spin correlations
become short-ranged, and the superconducting phase transition is controlled by
spin excitations. I will stress that the pseudogap phenomenon naturally emerges
as a crossover between the antiferromagnetic and superconducting phases. As a
characteristic of non Fermi liquid, the mutual statistical interaction between
the spin and charge degrees of freedom will reach a maximum in a
high-temperature "strange metal phase" of the doped Mott insulator.Comment: 12 pages, 12 figure
Freezing of anisotropic spin clusters in La1.98Sr0.02CuO4
A spin-glass compound, LaSrCuO, shows
quasi-three-dimensional magnetic ordering below 40 K. A remarkable
feature is that the magnetic correlation length along the orthorhombic
axis is much longer than that along the axis,
suggesting that the spin structure is closely related to the diagonal stripe
structure. The spin-glass state can be expressed as a random freezing of
quasi-three-dimensional spin clusters with anisotropic spin correlations
( \AA, \AA, and \AA at 1.6 K).
The new magnetic state is important as an intermediate phase between the
three-dimensional antiferromagnetic ordered phase in LaCuO and the
incommensurate phase in LaSrCuO in which the positions of
the incommensurate peaks are rotated by 45 in reciprocal space about
(,) from those observed in the superconducting LaCuO
compounds.Comment: 7 pages, RevTex, 8 PS figures, submitted to Phys. Rev.
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