Two-lifetime model for the cuprates revisited

Several models of the strange-metal state of the cuprate superconductors postulate the existence of strong inelastic forward scattering of the electrons, but direct evidence of such scattering is missing. Here we show that angle-resolved photoemission spectroscopy (ARPES) provides a unique tool which can address this issue. We propose a two-lifetime phenomenological model of the superconducting state of the cuprates and we show that it explains several salient low-energy features of the measured ARPES spectra. The model enables discrimination between forward- and large-angle scattering and, in addition, gives access to the magnitude of the gap function away from the Fermi surface.

💡 Research Summary

The paper addresses a long‑standing problem in the cuprate high‑temperature superconductors: the nature and magnitude of inelastic forward (small‑angle) scattering versus large‑angle (pair‑breaking) scattering, which are both thought to play a role in the strange‑metal state but have never been directly distinguished experimentally. The authors propose that angle‑resolved photoemission spectroscopy (ARPES) in the superconducting state provides a unique window onto these two scattering channels.

To this end they develop a phenomenological “momentum‑resolved Dynes phenomenology” (MRDP), which generalizes the well‑known Dynes formula for the density of states. In MRDP each momentum k is assigned three local parameters: the superconducting gap Δ(k), a pair‑conserving scattering rate Γₛ(k) (forward scattering), and a pair‑breaking scattering rate Γ(k) (large‑angle scattering). Starting from the Green’s function derived in Refs.