Spin charge sepration in the doped frustrated J1-J2-J3 Heisenberg antiferromagnet on the square lattice

We study undoped and doped frustrated J1-J2-J3 Heisenberg antiferromagnet on the square lattice using both exact diagonalization techniques and projections onto the short-range RVB subspace. The insulating system shows, in the vicinity of the $(J_3+J_2)/J_1 =0.5$ line, a magnetically disordered ground very well captured by a RVB wave function. The nature, dimer liquid or valence bond crystal, of such a RVB phase is characterized from the computation of dimer-dimer correlations and a singlet spectrum analysis of finite clusters up to 50 sites. We also show that a substancial reduction of the quasi-particle spectral weight of a doped hole can be related to the spin liquid character of the magnetic background. This suggests that spin-charge separation occurs in such a frustrated system.