378 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
2D orbital-like magnetic order in
In high temperature copper oxides superconductors, a novel magnetic order
associated with the pseudogap phase has been identified in two different
cuprate families over a wide region of temperature and doping. We here report
the observation below 120 K of a similar magnetic ordering in the archetypal
cuprate (LSCO) system for x=0.085. In contrast to the
previous reports, the magnetic ordering in LSCO is {\it\bf only} short range
with an in-plane correlation length of 10 \AA\ and is bidimensional
(2D). Such a less pronounced order suggests an interaction with other
electronic instabilities. In particular, LSCO also exhibits a strong tendency
towards stripes ordering at the expense of the superconducting state.Comment: 4 figures, submitted to Phys. Rev. Let
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
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
Correlated decay of triplet excitations in the Shastry-Sutherland compound SrCu(BO)
The temperature dependence of the gapped triplet excitations (triplons) in
the 2D Shastry-Sutherland quantum magnet SrCu(BO) is studied by
means of inelastic neutron scattering. The excitation amplitude rapidly
decreases as a function of temperature while the integrated spectral weight can
be explained by an isolated dimer model up to 10~K. Analyzing this anomalous
spectral line-shape in terms of damped harmonic oscillators shows that the
observed damping is due to a two-component process: one component remains sharp
and resolution limited while the second broadens. We explain the underlying
mechanism through a simple yet quantitatively accurate model of correlated
decay of triplons: an excited triplon is long-lived if no thermally populated
triplons are near-by but decays quickly if there are. The phenomenon is a
direct consequence of frustration induced triplon localization in the
Shastry--Sutherland lattice.Comment: 5 pages, 4 figure
Exotic Kondo crossover in a wide temperature region in the topological Kondo insulator SmB6 revealed by high-resolution ARPES
Temperature dependence of the electronic structure of SmB6 is studied by
high-resolution ARPES down to 1 K. We demonstrate that there is no essential
difference for the dispersions of the surface states below and above the
resistivity saturating anomaly (~ 3.5 K). Quantitative analyses of the surface
states indicate that the quasi-particle scattering rate increases linearly as a
function of temperature and binding energy, which differs from Fermi-Liquid
behavior. Most intriguingly, we observe that the hybridization between the d
and f states builds gradually over a wide temperature region (30 K < T < 110
K). The surface states appear when the hybridization starts to develop. Our
detailed temperature-dependence results give a complete interpretation of the
exotic resistivity result of SmB6, as well as the discrepancies among
experimental results concerning the temperature regions in which the
topological surface states emerge and the Kondo gap opens, and give new
insights into the exotic Kondo crossover and its relationship with the
topological surface states in the topological Kondo insulator SmB6.Comment: 8 pages, 5 figure
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