CMP Seminar: Kagome superconductivity: conventional or unconventional?

Unconventional superconductivity is often referred to as originating from a pairing mechanism different from electron-phonon interactions and connected to an anisotropic superconducting order parameter with sign change and higher angular momentum of the Cooper pair wavefunction. A number of spectroscopic probes are used experimentally to examine the symmetry and the (relative) sign of the order parameter. These include local spectroscopy on nonmagnetic impurities, inelastic neutron scattering in the superconducting state and nuclear magnetic resonance (NMR).
Kagome metals have been in the focus of recent research due to the multiple observed phases such as charge density wave and superconductivity together with evidences of time reversal symmetry breaking [1]. For superconductivity on the kagome lattice, the conclusions that can be drawn from experimental data deviate due to particular band structure effects associated with sublattice interference: Even unconventional gap structure which sums to zero over the Fermi surface, remains robust to disorder and exhibits a Hebel-Slichter peak in the temperature-dependent spin-relaxation rate. These results imply that unconventional superconductivity on the kagome lattice may appear similar to conventional non-sign-changing superconductivity in the mentioned spectroscopic probes and experimental data has to be re-interpreted [2, 3].

[1] Hanbin Deng, et al., Evidence for time-reversal symmetry-breaking kagome superconductivity, Nature Materials (2024)
[2] Sofie Castro Holbæk, Morten H. Christensen, Andreas Kreisel, Brian M. Andersen, Phys. Rev. B 108, 144508 (2023)
[3] Yi Dai, Andreas Kreisel, Brian M. Andersen, Phys. Rev. B 110, 144516 (2024)

The link to the Simpkins Lee Seminar Room is:  https://zoom.us/j/4862374566