In recent years, reliable approaches have been developed [1] to identify the dominant fluctuations driving the multifaceted phenomena of many-electron physics. Among those, the “fluctuation diagnostics" [2] was hitherto applied only to normal, paramagnetic phases, allowing to pinpoint the spin-fluctuation nature of the pseudogap occurring in the two-dimensional Hubbard model [1-2]. After extending the approach to the superconducting phase [3], we were able to identify antiferromagnetic fluctuations as the "pairing glue" of d-wave superconductivity both in the underdoped and the overdoped regime of the Hubbard model. However, the predominant magnetic fluctuations might significantly differ [4] from those of conventional spin-fluctuation theory.
[1] T. Schäfer and A. Toschi, Journal of Physics: Condensed Matter 33, 214001 (2021).
[2] O. Gunnarsson et al., Phys. Rev. Lett. 114, 236402 (2015).
[3] Xinyang Dong, L. Del Re, A. Toschi and E. Gull, PNAS 119 e2205048119 (2022).
[4] F. Krien, P. Worm, P. Chalupa-Gantner, A. Toschi and K. Held, Comm. Phys. 5, 336 (2022).
