63Cu NQR/NMR Study of Zn-SubstitutedYBa2Cu4O8–Effect of Impurity on Spin-Gap-Like Behavior–

Zheng, Guojun; Odaguchi, T.; Mito, T.; Kitaoka, Y.; Asayama, Kunisuke; Kodama, Y.

doi:10.1143/jpsj.62.2591

Cited by 84 publications

(49 citation statements)

References 22 publications

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“…Further doping to 1.275 % zinc has the interesting effect of completely suppressing superconductivity and eliminating any gap-like structure in the scattering rate spectra, which makes them look very much like the spectra in the normal state of optimally doped YBCO where the neutron mode is absent. Similar effects are found by Zheng et al in NMR experiments on YBCO-124 doped with zinc [100,101]. While Zn doping has a relatively small effect on the Knight shift, it completely suppresses the pseudogap in the spin relaxation rate already at the 1% doping level.…”

Section: The Pseudogap and The Ab Plane Scattering Ratesupporting

confidence: 84%

The mysterious pseudogap in high temperature superconductors: an infrared view

Timusk

2003

Solid State Communications

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We review the contribution of infrared spectroscopy to the study of the pseudogap in high temperature superconductors. The pseudogap appears as a depression of the frequency dependent conductivity in the c-axis direction and seems to be related to a real gap in the density of states. It can also be seen in the Knight shift, photoemission and tunneling experiments. In underdoped samples it appears near room temperature and does not close with temperature. Another related phenomenon that has been studied by infrared is the depression in the ab-plane scattering rate. Two separate effects can be discerned. At high temperatures there is broad depression of scattering below 1000 cm −1 which may be related to the gap in the density of states. At a lower temperature a sharper structure is seen, which appears to be associated with scattering from a mode at 300 cm −1 , and which governs the carrier life time at low temperatures. This mode shows up in a number of other experiments, as a kink in ARPES dispersion, and a resonance at 41 meV in magnetic neutron scattering. Since the infrared technique can be used on a wide range of samples it has provided evidence that the scattering mode is present in all high temperature cuprates and that its frequency in optimally doped materials scales with the superconducting transition temperature. The lanthanum and neodymium based cuprates do not follow this scaling and appear to have depressed transition temperatures.

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Section: The Pseudogap and The Ab Plane Scattering Ratesupporting

confidence: 84%

The mysterious pseudogap in high temperature superconductors: an infrared view

Timusk

2003

Solid State Communications

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“…In Zn-doped YBCO, the spin-lattice relaxation rate of 63 Cu nuclei (1/ 63 T 1 ) does not show the characteristic drop observed below 150 K in pure samples (pseudogap behavior), but continues to increase with decreasing T [1,3,10,18]. WK correctly point out that this increase does not necessarily imply an enhancement of AF correlations.…”

Section: Cu Nqr T1mentioning

confidence: 95%

Comment on “Localized behavior near the Zn impurity inYBa2Cu4O8as measured by nuclear quadrupole resonance”

Julien¹,

Tokunaga²,

Fehér³

et al. 2005

Phys. Rev. B

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Williams and Krämer [Phys. Rev. B 64, 104506 (2001)] have recently argued against the existence of staggered magnetic moments residing on several lattice sites around Zn impurities in YBCO superconductors. This claim, which is in line with an earlier publication by Williams, Tallon and Dupree [Phys. Rev. B 61, 4319 (2000)], is however in contradiction with a large body of experimental data from different NMR groups. On the contrary, the authors argue in favor of a very localized spin and charge density on Cu sites first neighbors to Zn. We show that the conclusions of Williams and Krämer arise from erroneous interpretations of NMR and NQR data.

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“…The valency of Zn is Zn 2+ (d 10 ) and compared with the Cu 2+ case one electron is trapped by one additional positive charge of the neucleus, which forms a singlet on the Zn site. In the underdoped cuprates with spin gap, it is found experimentally that a local moment of S = 1/2 appears on neighboring Cu sites [2][3][4][5][6][7][8][9][10][11]. We believe this localized spin is not screened by the conduction electron spins because of the reduced density of states for spins at the Fermi energy E F in the presence of the spin gap [12,13].…”

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confidence: 99%