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- Title
An unusual isotope effect in a high-transition-temperature superconductor.
- Authors
Gweon, G.-H.; Sasagawa, T.; Zhou, S. Y.; Graf, J.; Takagi, H.; Lee, D.-H.; Lanzara, A.
- Abstract
In conventional superconductors, the electron pairing that allows superconductivity is caused by exchange of virtual phonons, which are quanta of lattice vibration. For high-transition-temperature (high-Tc) superconductors, it is far from clear that phonons are involved in the pairing at all. For example, the negligible change in Tc of optimally doped Bi2Sr2CaCu2O8+d (Bi2212; ref. 1) upon oxygen isotope substitution (16O ? 18O leads to Tc decreasing from 92 to 91?K) has often been taken to mean that phonons play an insignificant role in this material. Here we provide a detailed comparison of the electron dynamics of Bi2212 samples containing different oxygen isotopes, using angle-resolved photoemission spectroscopy. Our data show definite and strong isotope effects. Surprisingly, the effects mainly appear in broad high-energy humps, commonly referred to as ‘incoherent peaks’. As a function of temperature and electron momentum, the magnitude of the isotope effect closely correlates with the superconducting gap-that is, the pair binding energy. We suggest that these results can be explained in a dynamic spin-Peierls picture, where the singlet pairing of electrons and the electron-lattice coupling mutually enhance each other.
- Subjects
SUPERCONDUCTIVITY; PHONONS; DYNAMICS; ELECTRONS; ISOTOPES
- Publication
Nature, 2004, Vol 430, Issue 6996, p187
- ISSN
0028-0836
- Publication type
Article
- DOI
10.1038/nature02731