Small tip angle NMR as a probe of electron-mediated nuclear spin-spin couplings in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YBa</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi><

Pennington, C. H.; Yu, Sisheng; Gorny, Krzysztof R.; Buoni, Matt; Hults, W. L.; Smith, J. L.

doi:10.1103/physrevb.63.054513

Cited by 5 publications

(4 citation statements)

References 53 publications

(82 reference statements)

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“…Among these problems the applicability of a one-band approach to describe the low-lying spin and charge excitations in these materials is of special importance. Several experiments [6,7,8] indicate that a second spin fluid with independent dynamics is required.…”

Section: Introductionmentioning

confidence: 99%

First-principles calculation of electric field gradients and hyperfine couplings in YBa2Cu3O7

et al. 2001

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Abstract. The local electronic structure of YBa2Cu3O7 has been calculated using first-principles cluster methods. Several clusters embedded in an appropriate background potential have been investigated. The electric field gradients at the copper and oxygen sites are determined and compared to previous theoretical calculations and experiments. Spin polarized calculations with different spin multiplicities have enabled a detailed study of the spin density distribution to be made and a simultaneous determination of magnetic hyperfine coupling parameters. The contributions from on-site and transferred hyperfine fields have been disentangled with the conclusion that the transferred spin densities essentially are due to nearest neighbour copper ions only with marginal influence of ions further away. This implies that the variant temperature dependencies of the planar copper and oxygen NMR spin-lattice relaxation rates are only compatible with commensurate antiferromagnetic correlations. The theoretical hyperfine parameters are compared with those derived from experimental data. PACS

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Section: Introductionmentioning

confidence: 99%

First-principles calculation of electric field gradients and hyperfine couplings in YBa2Cu3O7

et al. 2001

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“…On the other hand, small-tip angle spin-echo double resonance measurements 90 find that the electron mediated nuclear-nuclear couplings between neighboring Cu-O and Cu-Cu are incompatible with one-component cuprate theories. In addition, the high-temperature Y spin relaxation and Knight shifts 91 are incompatible with one-component cuprate theories.…”

Section: Nmrmentioning

confidence: 97%

Chiral plaquette polaron theory of cuprate superconductivity

Tahir-Kheli

Goddard

2007

Phys. Rev. B

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Ab initio density functional calculations on explicitly doped La 2−x Sr x CuO 4 find that doping creates localized holes in out-of-plane orbitals. A model for cuprate superconductivity is developed based on the assumption that doping leads to the formation of holes on a four-site Cu plaquette composed of the out-of-plane A 1 orbitals apical O p z , planar Cu d 3z 2 −r 2, and planar O p . This is in contrast to the assumption of hole doping into planar Cu d x 2 −y 2 and O p orbitals as in the t-J model. Allowing these holes to interact with the d 9 spin background leads to chiral polarons with either a clockwise or anticlockwise charge current. When the polaron plaquettes percolate through the crystal at x Ϸ 0.05 for La 2−x Sr x CuO 4 , a Cu d x 2 −y 2 and planar O p band is formed. The computed percolation doping of x Ϸ 0.05 equals the observed transition to the "metallic" and superconducting phase for La 2−x Sr x CuO 4 . Spin exchange Coulomb repulsion with chiral polarons leads to d-wave superconducting pairing. The equivalent of the Debye energy in phonon superconductivity is the maximum energy separation between a chiral polaron and its time-reversed partner. This energy separation is on the order of the antiferromagnetic spin coupling energy, J dd ϳ 0.1 eV, suggesting a higher critical temperature. An additive skew-scattering contribution to the Hall effect is induced by chiral polarons and leads to a temperature dependent Hall effect that fits the measured values for La 2−x Sr x CuO 4 . The integrated imaginary susceptibility, observed by neutron spin scattering, satisfies / T scaling due to chirality and spin-flip scattering of polarons along with a uniform distribution of polaron energy splittings. The derived functional form is compatible with experiments. The static spin structure factor for chiral spin coupling of the polarons to the undoped antiferromagnetic Cu d 9 spins is computed for classical spins on large two-dimensional lattices and is found to be incommensurate with a separation distance from ͑ / a , / a͒ given by ␦Q Ϸ͑2 / a͒x, where x is the doping.When the perturbed x 2 − y 2 band energy in mean field is included, incommensurability along the Cu-O bond direction is favored. A resistivity ϳT +1 arises when the polaron energy separation density is of the form ϳ⌬ due to Coulomb scattering of the x 2 − y 2 band with polarons. A uniform density leads to linear resistivity. The coupling of the x 2 − y 2 band to the undoped Cu d 9 spins leads to the angle-resolved photoemission pseudogap and its qualitative doping and temperature dependence. The chiral plaquette polaron leads to an explanation of the evolution of the bilayer splitting in Bi-2212.

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“…That is, irreversible dephasing of the spins involved in the echo formation results as a direct consequence of the application of P 2 in the two-pulse spin-echo sequence. Although it is known that spin-echo decays in an inhomogeneously broadened NMR line can depend on the pulses applied when nuclear spin-spin coupling is significant [12,13,14], by adding a third pulse (hereafter referred to as P nr ) whose frequency differs from the NMR frequency we are able to rule it out as the source for our observations. The results are interpreted as evidence for the formation of an inhomogeneous electronic state that couples to the rf pulses.…”

mentioning

confidence: 99%

“…Then, pulse-induced spin flips of coupled neighbors alter the local magnetic field with the application of P 2, thus diminishing the echo-refocusing. The echo decay is a function of the probability that neighboring spins are flipped by the action of P 2 [14], which can be written as P (θ 2 ) ∝ sin 2 (θ 2 /2), as long as B ef f 1 = αB 1 > ∆ and t −1 w2 < ∆, where ∆ characterizes the linewidth. Therefore, it is expected that if internuclear coupling governs the spin echo decay, the rate varies as a function of P (θ 2 ) only.…”

mentioning

confidence: 99%

Inhomogeneous Electronic Structure Probed by Spin-Echo Experiments in the Electron Doped High-TcSuperconductorPr1.85
Zámborszky
¹
,
Wu
²
,
Shinagawa
³

et al. 2004
Phys. Rev. Lett.

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63 Cu nuclear magnetic resonance (NMR) spin-echo decay rate (T −1 2 ) measurements are reported for the normal and superconducting states of a single crystal of Pr1.85Ce0.15CuO4−y (PCCO) in a magnetic field B0 = 9 T over the temperature range 2 K< T <200 K. The spin-echo decay rate is temperature-dependent for T < 55 K, and has a substantial dependence on the radio frequency (rf) pulse parameters below T ≈ 25 K. This dependence indicates that T −1 2 is strongly effected by a local magnetic field distribution that can be modified by the rf pulses, including ones that are not at the nuclear Larmor frequency. The low-temperature results are consistent with the formation of a static inhomogeneous electronic structure that couples to the rf fields of the pulses.

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Small tip angle NMR as a probe of electron-mediated nuclear spin-spin couplings inYBa2Cu3O<

Cited by 5 publications

References 53 publications

First-principles calculation of electric field gradients and hyperfine couplings in YBa2Cu3O7

First-principles calculation of electric field gradients and hyperfine couplings in YBa2Cu3O7

Chiral plaquette polaron theory of cuprate superconductivity

Inhomogeneous Electronic Structure Probed by Spin-Echo Experiments in the Electron Doped High-TcSuperconductorPr1.85
Zámborszky
¹
,
Wu
²
,
Shinagawa
³

et al. 2004
Phys. Rev. Lett.

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Small tip angle NMR as a probe of electron-mediated nuclear spin-spin couplings inYBa2Cu3O<

Cited by 5 publications

References 53 publications

First-principles calculation of electric field gradients and hyperfine couplings in YBa2Cu3O7

First-principles calculation of electric field gradients and hyperfine couplings in YBa2Cu3O7

Chiral plaquette polaron theory of cuprate superconductivity

Inhomogeneous Electronic Structure Probed by Spin-Echo Experiments in the Electron Doped High-TcSuperconductorPr1.85Zámborszky1, Wu2, Shinagawa3 et al. 2004Phys. Rev. Lett.

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Product

Resources

About

Inhomogeneous Electronic Structure Probed by Spin-Echo Experiments in the Electron Doped High-TcSuperconductorPr1.85
Zámborszky
¹
,
Wu
²
,
Shinagawa
³

et al. 2004
Phys. Rev. Lett.