Evidence for precursor superconducting pairing above T-c in underdoped cuprates from an analysis of the in-plane infrared response

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This publication doesn't include Faculty of Medicine. It includes Central European Institute of Technology. Official publication website can be found on muni.cz.


Year of publication 2015
Type Article in Periodical
Magazine / Source New Journal of Physics
MU Faculty or unit

Central European Institute of Technology

Web http://iopscience.iop.org/article/10.1088/1367-2630/17/5/053022
Doi http://dx.doi.org/10.1088/1367-2630/17/5/053022
Field Solid matter physics and magnetism
Keywords cuprate superconductors; infrared response; precursor superconducting pairing above T-c
Description We performed calculations of the in-plane infrared response of underdoped cuprate superconductors to clarify the origin of a characteristic dip feature which occurs in the published experimental spectra of the real part of the in-plane conductivity below an onset temperature T-ons considerably higher than T-c. We provide several arguments, based on a detailed comparison of our results with the published experimental data, confirming that the dip feature and the related features of the memory function M(omega)= M1(omega)+ iM2(omega)(a peak in M1 and a kink in M2) are due to superconducting pairing correlations that develop below T-ons. In particular, we show that (i) the dip feature, the peak and the kink of the low-temperature experimental data can be almost quantitatively reproduced by calculations based on a model of a d-wave superconductor. The formation of the dip feature in the experimental data below T-ons is shown to be analogous to the one occurring in the model spetra below T-c. (ii) Calculations based on simple models, for which the dip in the temperature range from T-c to T-ons is unrelated to superconducting pairing, predict a shift of the onset of the dip at the high-energy side upon entering the superconducting state, that is not observed in the experimental data; (iii) the conductivity data in conjunction with the recent photoemission data (Reber et al 2012 Nat. Phys. 8 606, Reber et al 2013 Phys. Rev. B 87 060506) imply the persistence of the coherence factor characteristic of superconducting pairing correlations in a range of temperatures above T-c.
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