Enhancement of superconductivity at the onset of charge-density-wave order in a metal

Abstract

We analyze superconductivity in the cuprates near the onset of an incommensurate charge-density-wave (CDW) order with momentum Q=(Q,0)/(0,Q), as observed in experiments. We first consider a semiphenomenological charge-fermion model in which hot fermions, separated by Q, attract each other by exchanging soft CDW fluctuations. We find that in a quantum-critical region near the CDW transition, Tc=Ag¯c, where g¯c is charge-fermion coupling and A is the prefactor, which we explicitly compute. We then consider the particular microscopic scenario in which the CDW order parameter emerges as a composite field made of primary spin-density-wave fields. We show that charge-fermion coupling g¯c is of the order of spin-fermion coupling g¯s. As a consequence, superconducting Tc is substantially enhanced near the onset of CDW order. Finally, we analyze the effect of an external magnetic field H. We show that, as H increases, the optimal Tc decreases and the superconducting dome becomes progressively more confined to the CDW quantum-critical point. These results are consistent with experiments.

Source-reported materials — not catalogue approval

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