Hot-lines topology and the fate of the spin resonance mode in three-dimensional unconventional superconductors

Fei Chen, Rafael M. Fernandes, Morten Christensen

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In the quasi-two-dimensional (quasi-2D) copper- and iron-based superconductors, the onset of superconductivity is accompanied by a prominent peak in the magnetic spectrum at momenta close to the wave-vector of the nearby antiferromagnetic state. Such a peak is well described in terms of a spin resonance mode, i.e., a spin-1 exciton theoretically predicted for quasi-2D superconductors with a sign-changing gap. The same theories, however, indicate that such a resonance mode should be absent in a three-dimensional (3D) system with a spherical Fermi surface. This raises the question of the fate of the spin resonance mode in layered unconventional superconductors that are not strongly anisotropic, such as certain heavy-fermion compounds and potentially the newly discovered nickelate superconductor NdNiO2. Here, we use the random phase approximation to calculate the dynamical spin susceptibility of 3D superconductors with a dx2-y2-wave gap symmetry and corrugated cylindrical-like Fermi surfaces. By varying the out-of-plane hopping anisotropy tz/t, we demonstrate that the appearance of a spin resonance mode is determined by the topology of the hot lines, i.e., lines on the Fermi surface that are connected by the magnetic wave vector. For an in-plane antiferromagnetic wave vector, the hot lines undergo a topological transition from open lines to closed loops at a critical tz/t value. The closed hot lines cross the nodal superconducting lines, making the spin resonance mode overdamped and incoherent. In contrast, for an out-of-plane antiferromagnetic wave vector, the hot lines remain open and the spin resonance mode remains sharp. We discuss the experimental implications of our results for the out-of-plane dispersion of the spin resonance mode and, more generally, for inelastic neutron scattering experiments on unconventional superconductors.

Original languageEnglish (US)
Article number014511
JournalPhysical Review B
Issue number1
StatePublished - Jul 1 2022

Bibliographical note

Funding Information:
We acknowledge useful discussions with A. V. Chubukov, A. Kreisel, and H. S. Røising. This work was supported by the U. S. Department of Energy through the University of Minnesota Center for Quantum Materials, under Grant No. DE-SC-0016371. The authors also acknowledge the Minnesota Supercomputing Institute at the University of Minnesota, where the numerical calculations were performed. M.H.C. also acknowledges support from a Carlsbergfondet fellowship.

Publisher Copyright:
© 2022 American Physical Society.


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