Dubroka, Adam Yu, Li Munzar, Dominik Kim, KyungWan Rössle, Matthias Malik, Vivek Kumar Lin, C.T. Keimer, B. Wolf, Th. Bernhard, Christian 2010-10-11 With the technique of infrared ellipsometry we performed a detailed study of the temperature- and doping dependence of the <i>c</i>-axis response of a series of YBa₂Cu₃O_7−δ single crystals. In particular, we explored the anomalous electronic properties at temperatures above the macroscopic superconducting transition temperature, <i>T</i> _c, whose conflicting explanations range from a precursor superconducting state to electronic correlations that compete with superconductivity. We show that the <i>c</i>-axis spectra provide evidence that both kinds of correlations are present and that their contributions can be disentangled based on an analysis with a so-called multilayer-model. We find that the onset temperature, <i>T</i> ^*, and the energy scale, Δ_PG, of the competing pseudogap increase rapidly towards the underdoped side whereas they vanish on the overdoped side. In addition, we provide evidence that in a strongly underdoped sample the precursor superconducting correlations develop below an onset temperature, <i>T</i> ^ons, that is considerably lower than <i>T</i> ^* but still much higher than <i>T</i> _c. application/pdf https://folia.unifr.ch/global/documents/301919 https://folia.unifr.ch/documents/301919/files/11734_2010_Article_1392.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1140/epjst/e2010-01298-7 info:eu-repo/semantics/openAccess License undefined The European Physical Journal - Special Topics. - 2010, vol. 188, no. 1, p. 73-88 info:eu-repo/classification/udc/53 Pseudogap and precursor superconductivity in underdoped cuprate high temperature superconductors: A far-infrared ellipsometry study http://purl.org/coar/resource_type/c_6501