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Originally published in Science Express on 4 June 2009
Science 26 June 2009:
Vol. 324. no. 5935, pp. 1689 - 1693
DOI: 10.1126/science.1174338
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Reports

Extending Universal Nodal Excitations Optimizes Superconductivity in Bi2Sr2CaCu2O8+{delta}

Aakash Pushp,1,2,* Colin V. Parker,1,* Abhay N. Pasupathy,1,{dagger} Kenjiro K. Gomes,1,{ddagger} Shimpei Ono,3 Jinsheng Wen,4 Zhijun Xu,4 Genda Gu,4 Ali Yazdani1,§

Understanding the mechanism by which d wave superconductivity in the cuprates emerges and is optimized by doping the Mott insulator is one of the major outstanding problems in condensed-matter physics. Our high-resolution scanning tunneling microscopy measurements of the high–transition temperature (Tc) superconductor Bi2Sr2CaCu2O8+{delta} show that samples with different Tc values in the low doping regime follow a remarkably universal d wave low-energy excitation spectrum, indicating a doping-independent nodal gap. We demonstrate that Tc instead correlates with the fraction of the Fermi surface over which the samples exhibit the universal spectrum. Optimal Tc is achieved when all parts of the Fermi surface follow this universal behavior. Increasing the temperature above Tc turns the universal spectrum into an arc of gapless excitations, whereas overdoping breaks down the universal nodal behavior.

1 Joseph Henry Laboratories and Department of Physics, Princeton University, Princeton, NJ 08544, USA.
2 Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
3 Central Research Institute of Electric Power Industry, Komae, Tokyo 201-8511, Japan.
4 Condensed Matter Physics and Materials Science, Brookhaven National Laboratory (BNL), Upton, NY 11973, USA.

* These authors contributed equally to this work.

{dagger} Present address: Department of Physics, Columbia University, New York, NY 10027, USA.

{ddagger} Present address: Department of Physics, Stanford University, Stanford, CA 94305, USA.

§ To whom correspondence should be addressed. E-mail: yazdani{at}princeton.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Chasing Arcs in Cuprate Superconductors.
M. R. Norman (2009)
Science 325, 1080-1081
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