NQR investigations of the high-Tc superconductor Ba2YCU3O7

Riesemeier, H.; Grabow, Ch.; Scheidt, E.‐W.; Müller, V.; Lüders, Klaus; Riegel, D.

doi:10.1016/0038-1098(87)90970-7

Cited by 73 publications

(10 citation statements)

References 20 publications

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“…Mali et al |6] were among the first who observed Cu NQR as well as NMR spectra in this superconductor. Others obtained very similar results [7][8][9][10][11] (1) where the asymmetry parameter rj -{V^^ -K|.,,)/F.. cannot separately be determined in zero field. It is therefore necessary to apply a high magnetic field S,,, where all four levels (/ = 3/2) are split.…”

Section: Structural Information From Quadrupole Spectrasupporting

confidence: 58%

Nuclear magnetic resonance in high-T_c superconductors

Mehring

1989

IBM J. Res. & Dev.

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This paper is aimed at the nonspecialist In nuclear magnetic resonance who wants to know what NMR can do to increase his understanding of high-r^ superconductors. IMost NIMR results are discussed in an illustrative manner to facilitate intuitive understanding. Several specific NMR experiments are presented which demonstrate the variety of this experimental technique. Special emphasis is given to the following aspects: ionic charges and quadrupole interaction, local fields and magnetic ordering, conduction electrons and Knight shifts, quasiparticle excitations, and nuclear spinlattice relaxation.

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Section: Structural Information From Quadrupole Spectrasupporting

confidence: 58%

Nuclear magnetic resonance in high-T_c superconductors

Mehring

1989

IBM J. Res. & Dev.

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“…Results and Discussion Figure 1 shows the temperature dependence of the zero-field NQR frequency v Q as obtained for the 63 Cu isotope as the Cu(l) site in YBa 2 Cu 3 0 7 _ (5 powdered samples. Within experimental errors the temperature dependence of v Q agrees with that of earlier measurements [4], Upon cooling, v Q decreases linearly down to T c . In the vicinity of T c , however, a discontinuous change of v Q is observed.…”

Section: Methodssupporting

confidence: 89%

“…For the Cu(l) sites (chain sites with a planar oxygen environment) v Q is about 22 MHz and for the Cu (2) sites (with a distorted pyramidal oxygen environment) v Q is about 31.5 MHz [1][2][3]. In the normal conducting state a linear temperature dependence of these two frequencies was found, but with opposite temperature coefficients [4,5]: with decreasing temperature the Cu(l) frequency decreases and the Cu(2) frequency increases. Up to now it is not clear whether this different behaviour is predominantly due to lattice vibrations or changes in the lattice parameters.…”

Section: Introductionmentioning

confidence: 92%

“…Up to now it is not clear whether this different behaviour is predominantly due to lattice vibrations or changes in the lattice parameters. In the vicinity of T c and in the superconducting state the situation is more complex, and different results have been published so far [4,5]. A general difficulty arises from the fact that the line intensities and signal-to-noise ratios are reduced considerably in this region.…”

Section: Introductionmentioning

confidence: 99%

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Temperature Dependence of the NQR Frequency and Linewidth of the High-J c Superconductor YBa 2 Cu 3 0 7 _ 5

Riesemeier

Pattloch

Scheidt

et al. 1990

Zeitschrift Für Naturforschung A

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For YBa 2 Cu 3 0 7 _ a powder samples of different average grain sizes the temperature dependences of 63 Cu NQR frequencies and signal intensities are reported for the Cu (1) site in a temperature range of 4 300 K. Both quantities show a non-monotonic behaviour in the vicinity of the superconduction transition temperature T c . In the superconducting state the line shape of the NQR signal in zero-field depends on the strength of the dc magnetic field applied during the cooling-procedure. The resulting linewidth yields information about the internal trapped magnetic field.

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“…In high-resolution dilatometry studies of twinned and untwinned LSCO crystals, instabilities in the range 40-60K (not reproducible in detail) were found in the twinned samples only, reinforcing the suggestion that these features are 'related to the relaxation of twin-induced internal stresses' [275]. The Cu NQR frequency also displays an anomaly at T c , suggestive of a structural modification [607,608,581]; however, such anomalies are found in conventional superconductors [607], although their origin is not understood.…”

Section: Anomalies At Tcmentioning

confidence: 69%

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

Markiewicz

1997

Journal of Physics and Chemistry of Solids

371

280

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The Van Hove singularity (VHS) provides a paradigm for the study of the role of peaks in the density of states (dos) on electronic properties. More importantly, it appears to play a major role in the physics of the high-Tc superconductors, particularly since recent photoemission studies have found that the VHS is close to the Fermi level in most of the high-Tc cuprates near the composition of optimum Tc. This paper offers a comprehensive survey of the VHS model, describing both theoretical properties and experimental evidence for the picture. Special topics discussed include a survey of the Fermi surfaces of the cuprates and related compounds, and an analysis of the reliability of the slave boson approach to correlation effects. While many properties of the cuprates can be qualitatively understood by a simple rigid-band-filling model, this is inadequate for more quantitative results, since correlation effects tend to pin the Fermi level near the VHS over an extended doping range, and can lead to a nanoscale phase separation. Furthermore, the peaks in the dos lead to competition from other instabilities, both magnetic and structural (related to charge density waves). A novel form of dynamic structural instability, involving dynamic VHS-Jahn-Teller effects has been predicted. Scattered through the literature, there is considerable experimental evidence for both nanoscale phase separation of holes, and for local, possibly dynamic, structural disorder. This review attempts to gather these results into a comprehensive database, to sort the results, and to see how they fit into the Van Hove scenario. Recent experiments on underdoped cuprates are found to provide a strong confirmation that the pseudogap is driven by a splitting of the VHS degeneracy.

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NQR investigations of the high-Tc superconductor Ba2YCU3O7

Cited by 73 publications

References 20 publications

Nuclear magnetic resonance in high-T_c superconductors

Nuclear magnetic resonance in high-T_c superconductors

Temperature Dependence of the NQR Frequency and Linewidth of the High-J c Superconductor YBa 2 Cu 3 0 7 _ 5

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

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NQR investigations of the high-Tc superconductor Ba2YCU3O7

Cited by 73 publications

References 20 publications

Nuclear magnetic resonance in high-Tc superconductors

Nuclear magnetic resonance in high-Tc superconductors

Temperature Dependence of the NQR Frequency and Linewidth of the High-J c Superconductor YBa 2 Cu 3 0 7 _ 5

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

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Nuclear magnetic resonance in high-T_c superconductors

Nuclear magnetic resonance in high-T_c superconductors