Multiple intertwined pairing states and temperature-sensitive gap anisotropy for superconductivity at a nematic quantum-critical point

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Abstract

The proximity of many strongly correlated superconductors to density-wave or nematic order has led to an extensive search for fingerprints of pairing mediated by dynamical quantum-critical (QC) fluctuations of the corresponding order parameter. Here we study anisotropic s-wave superconductivity induced by anisotropic QC dynamical nematic fluctuations. We solve the non-linear gap equation for the pairing gap Δ (θ, ωm) and show that its angular dependence strongly varies below Tc. We show that this variation is a signature of QC pairing and comes about because there are multiple s-wave pairing instabilities with closely spaced transition temperatures Tc , n. Taken alone, each instability would produce a gap Δ (θ, ωm) that changes sign 8 n times along the Fermi surface. We show that the equilibrium gap Δ (θ, ωm) is a superposition of multiple components that are nonlinearly induced below the actual Tc= Tc , 0, and get resonantly enhanced at T=Tc,n<Tc. This gives rise to strong temperature variation of the angular dependence of Δ (θ, ωm). This variation progressively disappears away from a QC point.

Original languageEnglish (US)
Article number55
Journalnpj Quantum Materials
Volume4
Issue number1
DOIs
StatePublished - Dec 1 2019

Bibliographical note

Funding Information:
We thank E. Berg, R. Fernandes, S. Kivelson, M.N. Gastiasoro, S. Lederer, and Y. Schattner for stimulating discussions. We thank the Minnesota Supercomputing Institute at the University of Minnesota for providing resources that assisted with this work. This work was supported by the NSF DMR-1523036.

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