Unbiased fluctuation diagnostics of the self-energy: pseudogap physics beyond spin fluctuations

Correlated electronic systems may give rise to multiple effective interactions, whose combined impact on quasiparticle properties can be difficult to disentangle. We introduce and apply an unambiguous decomposition of the electronic self-energy, which allows us to quantify the contribution of various effective interactions simultaneously. We use this tool to revisit the hole-doped Hubbard model at strong coupling within the dynamical cluster approximation, where spin fluctuations have been identified as the origin of the pseudogap. While our fluctuation diagnostics confirms that spin fluctuations indeed suppress antinodal electronic spectral weight, we show that they alone can not capture the pseudogapped self-energy quantitatively. Other nonlocal Feynman diagrams yield substantial contributions and are needed for a quantitative description of the pseudogap.