Publication details

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



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

Central European Institute of Technology

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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