Pseudogap and precursor superconductivity in underdoped cuprate high temperature superconductors: A far-infrared ellipsometry study

Abstract

Abstract. With the technique of infrared ellipsometry we performed a detailed study of the temperature-and doping dependence of the c-axis response of a series of YBa 2Cu3O7−δ single crystals. In particular, we explored the anomalous electronic properties at temperatures above the macroscopic superconducting transition temperature, T c, whose conflicting explanations range from a precursor superconducting state to electronic correlations that compete with superconductivity. We show that the c-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, T * , and the energy scale, ΔPG, 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, T ons , that is considerably lower than T * but still much higher than Tc.

Superconducting and pseudogap effects on the interplane conductivity and Raman scattering cross section in the two-dimensional Hubbard model

“…2 of Ref. 48). Second, in optimal and overdoped materials the superconductivityinduced changes correspond to a strong decrease in the absorption at frequencies below ∼ 1000cm −1 with only a weak increase at higher frequencies > 1000cm −1 .…”

“…In bilayer systems such as YBa 2 Cu 3 O 6+x the inter-bilayer coupling has the form given by Eq. 10 but the intra-bilayer coupling may also have contributions from the zone diagonal electrons 48 . These complications will not be addressed in this paper.…”

Comparative analysis of tunneling magnetoresistance in low-TcNb/Al-AlOx/Nb and high-TcBiKrasnov1, Motzkau2, Golod3 et al. 2011Phys. Rev. B236500View full textAdd to dashboardCite

“…14 The c-axis transport in Bi-2212 is nonmetallic due to interlayer tunneling mechanism of transport, in combination with the so-called c-axis pseudogap. The latter is much more pronounced than the PG in the ab-plane transport 4,9,65 and exists in a broader temperature 7,14 and doping ranges. 6 In Ref.…”

“…A similar conclusion about the existence of two distinct pseudogaplike phenomena above T c was also reached in optical infrared ellipsometry studies. 9,65 The PG complicates analysis of tunneling magnetoresistance because it makes the superconducting transition fuzzy. Since the main purpose of this work is to establish how to extract unambiguous information out of magnetotunneling data, here we will mostly concentrate on analysis of overdoped Bi(Pb)-2212 crystals, which according to previous studies are less affected by the PG and are most close to the conventional BCS-type superconductivity.…”

Superconductivity in copper-oxygen compounds

“…There are many experimental indications that the rotational symmetry is broken and that the electronic states partially reconstruct due to incipient charge order driven by the strong correlations. The contribution of superconducting fluctuations to the pseudogap is small as can be seen independently from the spectral weight redistribution in the optical conductivity [200]. (ii) As soon as the order becomes static superconductivity is quenched.…”