(Ir)Relevance of Disorder for Superconductivity in Cuprates

Abstract

In cuprates that exhibit high-temperature superconductivity (HTS), as the doping level p is increased beyond the optimal value, the superfluid density ns0 decreases and eventually vanishes, closely tracking the critical temperature Tc. This has been interpreted using a dirty-d-wave extension of the Bardeen-Cooper-Schrieffer theory, assuming that Tc and ns0 decrease with increasing disorder and pair breaking. To test this hypothesis, we tuned the doping level in overdoped La2-xSrxCuO4−δ films by electrolyte gating, measured several parameters used to quantify the level of disorder (the residual resistivity ratio RRR, the mean free path l0, and the electron mobility μ), and studied how Tc and ns0 scale with these. The experimentally measured dependence turned out to be the opposite of the expected—Tc and ns0 increased with increasing disorder. This brings the question of the true origin of the demise of Tc and ns0 with overdoping back to the center stage of the quest to decipher the HTS enigma.

Source-reported materials — not catalogue approval

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