Spinon deconfinement in doped frustrated quantum antiferromagnets

The confinement of a spinon liberated by doping two-dimensional frustrated quantum antiferromagnets with a nonmagnetic impurity or a mobile hole is investigated. For a static vacancy, an intermediate behavior between complete deconfinement (kagome) and strong confinement (checkerboard) is identified in the J₁--J₂--J₃ model on the square lattice, with the emergence of two length scales, a spinon confinement length larger than the magnetic correlation length. For mobile holes, this translates into an extended spinon-holon boundstate allowing one to bridge momentum (angular-resolved photoemission spectroscopy spectral function) and real-space (scanning tunneling microscopy) experimental observations. These features provide clear evidence for a nearby ``deconfined critical point'' in a doped microscopic model.