485 research outputs found
Correlation between oxygen isotope effects on the transition temperature and the magnetic penetration depth in high-temperature superconductors close to optimal doping
The oxygen-isotope (^{16}O/^{18}O) effect (OIE) on the in-plane magnetic
penetration depth \lambda_{ab}(0) in optimally-doped YBa_2Cu_3O_{7-\delta} and
La_{1.85}Sr_{0.15}CuO_4, and in slightly underdoped YBa_2Cu_4O_8 and
Y_{0.8}Pr_{0.2}Ba_2Cu_3O_{7-\delta} was studied by means of muon-spin rotation.
A substantial OIE on \lambda_{ab}(0) with an OIE exponent
\beta_O=-d\ln\lambda_{ab}(0)/d\ln M_O\approx - 0.2 (M_O is the mass of the
oxygen isotope), and a small OIE on the transition temperature T_c with an OIE
exponent \alpha_O=-d\ln T_{c}/d \ln M_O\simeq0.02 to 0.1 were observed. The
observation of a substantial isotope effect on \lambda_{ab}(0), even in
cuprates where the OIE on T_c is small, indicates that lattice effects play an
important role in cuprate HTS.Comment: 6 pages, 4 figure
Direct observation of impurity-induced magnetism in an S = 1/2 antiferromagnetic Heisenberg 2-leg spin ladder
Nuclear magnetic resonance and magnetization measurements were used to probe
the magnetic features of single-crystalline Bi(Cu(1-x)Znx)2PO6 with 0<x<0.05 at
temperatures between 2.6 K and 300 K. The simple lineshape of the 31P NMR
signals of the pristine compound changes considerably for x>0 and we present
clear evidence for a temperature dependent variation of the local magnetization
close to the Zn sites. The generic nature of this observation is indicated by
results of model calculations on appropriate spin systems of limited size
employing QMC methods.Comment: 4 pages, 4 figure
Oxygen-isotope effect on the superconducting gap in the cuprate superconductor Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta}
The oxygen-isotope (^{16}O/^{18}O) effect (OIE) on the zero-temperature
superconducting energy gap \Delta_0 was studied for a series of
Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta} samples (0.0\leq x\leq0.45). The OIE on
\Delta_0 was found to scale with the one on the superconducting transition
temperature. These experimental results are in quantitative agreement with
predictions from a polaronic model for cuprate high-temperature superconductors
and rule out approaches based on purely electronic mechanisms.Comment: 5 pages, 3 figure
Spin anisotropy of the resonance in superconducting FeSe0.5Te0.5
We have used polarized-neutron inelastic scattering to resolve the spin
fluctuations in superconducting FeSe0.5Te0.5 into components parallel and
perpendicular to the layers. A spin resonance at an energy of 6.5 meV is
observed to develop below T_c in both fluctuation components. The resonance
peak is anisotropic, with the in-plane component slightly larger than the
out-of-plane component. Away from the resonance peak the magnetic fluctuations
are isotropic in the energy range studied. The results are consistent with a
dominant singlet pairing state with s^{\pm} symmetry, with a possible minority
component of different symmetry.Comment: 5 pages, 4 figure
Magnetic field dependence of the oxygen isotope effect on the magnetic penetration depth in hole-doped cuprate superconductors
The magnetic field dependence of the oxygen-isotope (^{16}O/^{18}O) effect
(OIE) on the in-plane magnetic field penetration depth \lambda_{ab} was studied
in the hole-doped high-temperature cuprate superconductors YBa_2Cu_4O_8,
Y_0.8Pr_0.2Ba_2Cu_3O_7-\delta, and Y_0.7Pr_0.3Ba_2Cu_3O_7-\delta. It was found
that \lambda_ab for the ^{16}O substituted samples increases stronger with
increasing magnetic field than for the ^{18}O ones. The OIE on \lambda_ab
decreases by more than a factor of two with increasing magnetic field from
\mu_0H=0.2 T to \mu_0H=0.6 T. This effect can be explained by the isotope
dependence of the in-plane charge carrier mass m^\ast_{ab}.Comment: 4 pages, two figure
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