Talk by Johan Chang, University of Cherbrooke, Canada – Niels Bohr Institute - University of Copenhagen

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Talk by Johan Chang, University of Cherbrooke, Canada

Authors: J. Chang, R. Daou, David LeBoeuf, Olivier Cyr-Choinire, Francis Laliberte, Nicolas Doiron-Leyraud, B. J. Ramshaw, Ruixing Liang, D. A. Bonn,W. N. Hardy & Louis Taillefer

The nature of the pseudogap phase is a central problem in the quest to understand high-Tc cuprate superconductors. A fundamental question is what symmetries are broken when that phase sets in below a temperature T^*. Here we report the observation of a large in-plane anisotropy of the Nernst effect in YBa_2Cu_3O_y that sets in precisely at T^*, throughout the doping phase diagram [1]. We show that the CuO chains of the orthorhombic lattice are not responsible for this anisotropy, which is therefore an intrinsic property of the CuO_2 planes. We conclude that the pseudogap phase is an electronic state which strongly breaks four-fold rotational symmetry.
[1] R. Daou et al., arXiv:0909.4430 and J. Chang et al., arXiv:0907.5039