Microscopic insights to ARPES spectra of doped quantum anti-ferromagnets

The phase diagram of cuprates, often modeled by the 2D Fermi Hubbard or $t-J$ model, remains poorly understood at low doping. Here we present new theoretical insights to the ARPES spectrum of quantum anti-ferromagnets at low doping: We argue that, at strong coupling $t \gg J$, the spectrum directly reflects the spectral function of a spinon which forms a universal bound state with the chargon created in the measurement. Our result is relevant to cuprates in the pseudogap regime: we interpret the the observed Fermi-arcs in a fractionalized Fermi liquid (FL*) picture and argue that the strongly suppressed spectral weight on the back-side of the hole pocket is a signature for the Dirac-fermion nature of the underlying spinons. We present DMRG calculations of the one-hole spectrum, which support the existence of the universal spinon-chargon bound state we assume at strong couplings. Our results are also relevant for the search of Dirac spinons in a larger class of frustrated quantum magnets.