The fate of pairing and spin-charge separation in the presence of long-range antiferromagnetism

Abstract

We present a numerical study of competing orders in the 1D t-J model with long-range RKKYlike staggered spin interactions. By circumventing the constraints imposed by Mermin-Wagner's theorem, this Hamiltonian can realize long-range Néel order at half-filling. We determine the full phase diagram as a function of the exchange and density using the density matrix renormalization group (DMRG) method. We show that pairing is disfavored and the AFM insulator and metallic phase are separated by a broad regime with phase segregation, while spin-charge separation reemerges at low densities. Upon doping, interactions induce a confining potential that binds holons and spinons into full fledged fermionic quasi-particles. We calculate the photoemission spectrum of the model, showing the appearance of a coherent quasi-particle band splitting away from the holonspinon continuum with a width determined by J that survives at finite doping. We discuss how this simple toy-model can teach us about the phenomenology of its higher dimensional counterpart.