2,312 research outputs found
Ab initio calculations of the hydrogen bond
Recent x-ray Compton scattering experiments in ice have provided useful
information about the quantum nature of the interaction between HO
monomers. The hydrogen bond is characterized by a certain amount of charge
transfer which could be determined in a Compton experiment. We use ab-initio
simulations to investigate the hydrogen bond in HO structures by
calculating the Compton profile and related quantities in three different
systems, namely the water dimer, a cluster containing 12 water molecules and
the ice crystal. We show how to extract estimates of the charge transfer from
the Compton profiles.Comment: 16 pages, 7 figures, to appear in Phys. Rev.
Resonant Inelastic X-Ray Scattering from Valence Excitations in Insulating Copper-Oxides
We report resonant inelastic x-ray measurements of insulating LaCuO
and SrCuOCl taken with the incident energy tuned near the Cu K
absorption edge. We show that the spectra are well described in a shakeup
picture in 3rd order perturbation theory which exhibits both incoming and
outgoing resonances, and demonstrate how to extract a spectral function from
the raw data. We conclude by showing {\bf q}-dependent measurements of the
charge transfer gap.Comment: minor notational changes, discussion of anderson impurity model
fixed, references added; accepted by PR
Identification of Non-unitary triplet pairing in a heavy Fermion superconductor UPt_3
A NMR experiment recently done by Tou et al. on a heavy Fermion
superconductor UPt is interpreted in terms of a non-unitary spin-triplet
pairing state which we have been advocating. The proposed state successfully
explains various aspects of the seemingly complicated Knight shift behaviors
probed for major orientations, including a remarkable d-vector rotation under
weak fields. This entitles UPt as the first example that a charged many
body system forms a spin-triplet odd-par ity pairing at low temperatures and
demonstrates unambiguously that the putative spin-orbit coupling in UPt is
weak.Comment: 4 pages, 2 eps figures, to be published in J. Phys. Soc. Jpn. 67
(1998) No.
Incommensurate lattice distortion in the high temperature tetragonal phase of La(Sr,Ba)CuO
We report incommensurate diffuse (ICD) scattering appearing in the
high-temperature-tetragonal (HTT) phase of La(Sr,Ba)CuO
with observed by the neutron diffraction technique. For
all compositions, a sharp superlattice peak of the low-temperature-orthorhombic
(LTO) structure is replaced by a pair of ICD peaks with the modulation vector
parallel to the CuO octahedral tilting direction, that is, the diagonal
Cu-Cu direction of the CuO plane, above the LTO-HTT transition temperature
. The temperature dependences of the incommensurability for all
samples scale approximately as , while those of the integrated intensity
of the ICD peaks scale as . These observations together with
absence of ICD peaks in the non-superconducting sample evince a
universal incommensurate lattice instability of hole-doped 214 cuprates in the
superconducting regime.Comment: 6 pages, 6 figure
Quantum skyrmions and the destruction of long-range antiferromagnetic order in the high-Tc superconductors La(2-x)Sr(x)CuO(4) and YBa(2)Cu(3)O(6+x)
We study the destruction of the antiferromagnetic order in the high-Tc
superconductors La(2-x)Sr(x)CuO(4) and YBa(2)Cu(3)O(6+x) in the framework of
the CP1-nonlinear sigma model formulation of the 2D quantum Heisenberg
antiferromagnet. The dopants are introduced as independent fermions with
appropriate dispersion relations determined by the shape of the Fermi surface.
The energy of skyrmion topological defects, which are shown to be introduced by
doping, is used as an order parameter for antiferromagnetic order. We obtain
analytic expressions for this as a function of doping which allow us to plot
the curves T_N(x_c)\times x_c and M(x)\times x, for both YBCO and LSCO, in good
quantitative agreement with the experimental data.Comment: 4 pages, revtex, 5 embeeded figure
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