ARPES as a Self-Energy Spectroscopy – Power Law Liquids, Planckian Scattering, Conversion of Correlations across Tc, and Positive Feedback Loops

Electronic correlation effects are the driving forces behind much of complex matter, but are typically difficult or impossible to directly access via experiment. We have made major strides in developing ARPES into a true spectroscopy of self-energies, here discussing how it is applied to the study of cuprate high Tc superconductors. One major topic includes the “strange metal” normal state with “Planckian” scattering and non-Fermi-liquid non-quasiparticle correlations or self-energies [1]. Another major topic is how these self-energies transform as the system enters the superconducting state – something that can now be directly and precisely determined with ARPES [2]. In particular, we show how the normal state strange-metal self-energies that are incoherent in nature are dramatically converted into highly coherent self-energy effects in the normal state that lead to stronger superconducting state renormalization. This conversion begins well above T_C at the onset of superconducting fluctuations and it greatly increases the number of states that can pair. Therefore, there is positive feedback––the superconductive pairing creates the conversion between incoherent and coherent correlations that in turn strengthens the pairing.

1. T. J. Reber et al. A unified form of low-energy nodal electronic interactions in hole-doped cuprate superconductors. Nat. Commun. 10, 5737 (2019)
2. Haoxiang Li et al. Coherent organization of electronic correlations as a mechanism to enhance and stabilize high temperature cuprate superconductivity, Nature Communications 9, 26 (2018)