Percolative nature of the direct-current paraconductivity in cuprate superconductors

Petar Popčević, Damjan Pelc, Yang Tang, Kristijan Velebit, Zachary Anderson, Vikram Nagarajan, Guichuan Yu, Miroslav Požek, Neven Barišić, Martin Greven

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15 Scopus citations


Despite extraordinary scientific efforts over the past three decades, the cuprate high-temperature superconductors continue to pose formidable challenges. A pivotal problem, essential for understanding both the normal and superconducting states, is to clarify the nature of the superconducting pre-pairing above the bulk transition temperature Tc. Different experimental probes have given conflicting results, in part due to difficulties in discerning the superconducting response from the complex normal-state behavior. Moreover, it has proven challenging to separate common properties of the cuprates from compound-specific idiosyncrasies. Here we investigate the paraconductivity—the superconducting contribution to the direct-current (dc) conductivity—of the simple-tetragonal model cuprate material HgBa2CuO4+δ. We are able to separate the superconducting and normal-state responses by taking advantage of the Fermi-liquid nature of the normal state in underdoped HgBa2CuO4+δ; the robust and simple quadratic temperature-dependence of the normal-state resistivity enables us to extract the paraconductivity above the macroscopic Tc with great accuracy. We find that the paraconductivity exhibits unusual exponential temperature dependence, and that it can be quantitatively explained by a simple superconducting percolation model. Consequently, the emergence of superconductivity in this model system is dominated by the underlying intrinsic gap inhomogeneity. Motivated by these insights, we reanalyze published results for two other cuprates and find exponential behavior as well, with nearly the same characteristic temperature scale. The universal intrinsic gap inhomogeneity is not only essential for understanding the supercoducting precursor, but will also have to be taken into account in the analysis of other bulk measurements of the cuprates.

Original languageEnglish (US)
Article number42
Journalnpj Quantum Materials
Issue number1
StatePublished - Dec 1 2018

Bibliographical note

Funding Information:
P.P. acknowledges funding by the Croatian Science Foundation Project No. IP-2016-06-7258. D.P. and M.P. acknowledge funding by the Croatian Science Foundation under Grant No. IP-11-2013-2729. The work at the TU Wien was supported by FWF project P27980-N36 and the European Research Council (ERC Consolidator Grant No. 725521). The work at the University of Minnesota was funded by the Department of Energy through the University of Minnesota Center for Quantum Materials under DESC-0016371.

Publisher Copyright:
© 2018, The Author(s).

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