Temperature-Dependent Ellipsometry Measurements of Partial Coulomb Energy in Superconducting Cuprates

Article Article scientifique Article Temperature-Dependent Ellipsometry Measurements of Partial Coulomb Energy in Superconducting Cuprates eng 2016 author Levallois Julien 686018 author Tran Michaël 565761 author Pouliot D. author Presura C. N. author Greene L. H. author Eckstein J. N. author Uccelli Johanie Fanny 700290 author Giannini Enrico 0000-0003-3536-4771 503364 author Gu G. D. author Leggett A. J. author Van Der Marel Dirk 0000-0001-5266-9847 135104 031027 10.1103/PhysRevX.6.031027 2160-3308 We performed an experimental study of the temperature and doping dependence of the energy-loss function of the bilayer and trilayer bismuth cuprates family. The primary aim is to obtain information on the energy stored in the Coulomb interaction between the conduction electrons, on the temperature dependence thereof, and on the change of Coulomb interaction when Cooper pairs are formed. We performed temperature-dependent ellipsometry measurements on several Bi2Sr2CaCu2O8−x single crystals: underdoped with Tc=60, 70, and 83 K; optimally doped with Tc=91 K; overdoped with Tc=84, 81, 70, and 58 K; as well as optimally doped Bi2Sr2Ca2Cu3O10+x with Tc=110 K. Our first observation is that, as the temperature drops through Tc, the loss function in the range up to 2 eV displays a change of temperature dependence as compared to the temperature dependence in the normal state. This effect at—or close to—Tc depends strongly on doping, with a sign change for weak overdoping. The size of the observed change in Coulomb energy, using an extrapolation with reasonable assumptions about its q dependence, is about the same size as the condensation energy that has been measured in these compounds. Our results therefore lend support to the notion that the Coulomb energy is an important factor for stabilizing the superconducting phase. Because of the restriction to small momentum, our observations do not exclude a possible significant contribution to the condensation energy of the Coulomb energy associated with the region of q around (π,π). Condensed Matter Physics Superconductivity Coulomb energy Ellipsometry Dewey 500.2 Swiss National Science Foundation project 200021 – 162628 CH 33 Département de physique de la matière quantique 131 false 785 Groupe Van der Marel Physical review. X 6 3 a970b6d7-dc60-4c3d-8fbf-7caf044b5b15 Article (Published version) Public PhysRevX.6.031027.pdf 4298799 application/pdf openAccess Faculté des sciences / Section de physique / Département de physique de la matière quantique

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Temperature-Dependent Ellipsometry Measurements of Partial Coulomb Energy in Superconducting Cuprates	Physical review. X			2016	1,396	326

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Uccelli, Johanie Fanny