Emergent Feshbach-like interactions in a doped Majumdar-Ghosh model

Experimental and numerical spectroscopy have revealed novel physics in anti-ferromagnets, in particular in frustrated and doped systems. The Majumdar-Ghosh (MG) model has an analytically known spin-disordered ground state of dimerized singlets as a result of magnetic frustration. Here we study the single-hole angle-resolved photoemission spectroscopy (ARPES) spectrum of an extended MG model, where we introduce a spin-density interaction that is experimentally accessible with ultracold molecules. We report a bound spinon-holon ground state and clear signatures of a spinon-holon molecule state and polarons in the ARPES spectrum at different magnetizations. We find an emergent Feshbach-like interaction upon tuning across the unbinding of the spinon and the holon. Our results provide new insights into the physics of dopants in frustrated t-J models.