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# Magnetic energy change available to superconducting condensation in optimally doped YBa2Cu3O6.95

## Abstract

Understanding the magnetic excitations in high-temperature (high-Tc) copper-oxide superconductors is important because they may mediate the electron pairing for superconductivity1,2. By determining the wavevector (Q) and energy (ħω) dependence of the magnetic excitations, it is possible to calculate the change in the exchange energy available to the superconducting condensation energy3,4,5. For the high-Tc superconductor YBa2Cu3O6+x, the most prominent feature in the magnetic excitations is the resonance6,7,8,9,10,11,12. Suggestions that the resonance contributes a major part of the superconducting condensation4,13 have not gained acceptance because the resonance is only a small portion of the total magnetic scattering12,13,14. Here, we report an extensive mapping of magnetic excitations for YBa2Cu3O6.95 (Tc93 K). Absolute intensity measurements of the full spectra allow us to estimate the change in the magnetic exchange energy between the normal and superconducting states, which is about 15 times larger than the superconducting condensation energy15,16—more than enough to provide the driving force for high-Tc superconductivity in YBa2Cu3O6.95.

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## Acknowledgements

We thank E. Dagotto, Z. Y. Wen and F. C. Zhang for helpful discussions. This work is supported by the US DOE Office of Science, Division of Materials Science, Basic Energy Sciences under contract No. DE-FG02-05ER46202 (H.W. and P.D.). Oak Ridge National Laboratory is supported by the US DOE under contract No. DE-AC05-00OR22725 with UT/Battelle LLC. S.M.H. is supported by the UK EPSRC. D.J.S. would like to acknowledge the Center for Nanophase Material Science at Oak Ridge National Laboratory for their support.

## Affiliations

1. ### Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA

• Hyungje Woo
•  & Pengcheng Dai
2. ### Center for Neutron Scattering, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

• Hyungje Woo
• , Pengcheng Dai
•  & H. A. Mook
3. ### H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, UK

• S. M. Hayden

• T. Dahm
5. ### Department of Physics, University of California, Santa Barbara, California 93106, USA

• D. J. Scalapino
6. ### ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK

• T. G. Perring

• F. Doğan

## Authors

### Competing interests

The authors declare no competing financial interests.

## Corresponding authors

Correspondence to Pengcheng Dai or H. A. Mook.

## PDF files

1. 1.

### DOI

https://doi.org/10.1038/nphys394

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