Two-channel physics in lightly doped antiferromagnetic Mott insulators: Signatures in two-hole spectroscopy

Understanding the collective behavior of strongly correlated electrons in the underdoped regime of cuprate compounds constitutes a major goal of modern many-body physics. Nevertheless, accurate descriptions for ground-state and low-energy physics of the paradigmatic Hubbard and t-J models in two dimensions have remained elusive. In this talk, we present numerical simulations of spectral functions in the lightly doped t-J model and find indications of two coupled bands emerging at low energies in the two-hole spectrum.

Based on our numerical results we develop a phenomenological theoretical description which employs a recently proposed two-channel model including magnetic polarons and tightly bound bipolaronic hole pairs. This model qualitatively describes all low-energy features of the two-hole spectra, and a quantitative comparison suggests that the two channels are strongly coupled in the t-J model, as expected in the vicinity of an emergent Feshbach resonance. Our work paves the way for a deeper understanding of strongly correlated fermions beyond the realm of single-particle Green's functions.