Glass-induced enhancement of superconducting Tc: Pairing via dissipative mediators

Abstract

With substantial evidence of glassy behavior in the phase diagram of high-Tc superconductors and its coexistence with superconductivity, we attempt to answer the following question: what are the properties of a superconducting state where the force driving Cooper pairing becomes dissipative? We find that when the bosonic mediator is local, dissipation acts to reduce the superconducting critical temperature (Tc). On the other hand, contrary to naïve expectations, Tc behaves nonmonotonically with dissipation for a nonlocal mediator—weakly dissipative bosons at different energy scales act coherently to give rise to an increase in Tc and eventually destroy superconductivity when the dissipation exceeds a critical value. The critical value occurs when dissipative effects become comparable to the energy scale associated with the spatial stiffness of the mediator, at which point Tc acquires a maximum. We outline consequences of our results to recent proton-irradiation experiments (M. Leroux et al., arXiv:1808.05984) on the cuprate superconductor La2−xBaxCuO4 (LBCO), which observe a disorder-induced increase in Tc even when the transition temperature of the proximate charge density wave (CDW) seems to be unaffected by irradiation. Our mechanism is a way to raise Tc that does not require a “tug-of-war” type scenario between two competing phases.

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