Effect of the pseudogap on suppressing high energy inelastic neutron scattering in superconducting YBa2Cu3O6.5

C. Stock; R. A. Cowley; W. J. L. Buyers; C. D. Frost; J. W. Taylor; D. Peets; R. Liang; D. Bonn; W. N. Hardy

doi:10.1103/PhysRevB.82.174505

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Effect of the pseudogap on suppressing high energy inelastic neutron scattering in superconducting YBa2Cu3O6.5

C. Stock, R. A. Cowley, W. J. L. Buyers, C. D. Frost, J. W. Taylor, D. Peets, R. Liang, D. Bonn, W. N. Hardy

DOI 10.1103/PhysRevB.82.174505 · Physical Review B

T1

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Abstract

We have measured the spin fluctuations in the YBa2Cu3O6.5 (YBCO6.5,Tc=59 K) superconductor at high-energy transfers above ∼100 meV. Within experimental error, the momentum dependence is isotropic at high energies, similar to that measured in the insulator for two-dimensional spin waves, and the dispersion extrapolates back to the incommensurate wave vector at the elastic position. This result contrasts with previous expectations based on measurements around 50 meV which were suggestive of a softening of the spin-wave velocity with increased hole doping. Unlike the insulator, we observe a significant reduction in the intensity of the spin excitations for energy transfers above ∼100 meV similar to that observed above ∼200 meV in the YBCO6.35 (Tc=18 K) superconductor as the spin waves approach the zone boundary. We attribute this high-energy scale with a second gap and find agreement with measurements of the pseudogap in the cuprates associated with electronic anomalies along the antinodal positions. In addition, we observe a sharp peak at around 400 meV whose energy softens with increased hole doping. We discuss possible origins of this excitation including a hydrogen-related molecular excitation and a transition of electronic states between d levels.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
YBa2Cu3O6.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	59	Pressure not reported	onset
YBa2Cu3O6.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	59	Pressure not reported	unknown
YBCO6.35 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	18	Pressure not reported	unknown
YBCO6.33 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8	Pressure not reported	unknown
La2CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
La2-xSrxCuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Tl2Ba2CuO6+δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Bi2Sr2CaCu2O8+δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
HgBa2CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
La1.875Ba0.125CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6	Pressure not reported	unknown