Magnetic-Field-Induced RVB State in the t-J Model
A. Fabricio Albuquerque, George Balster Martins
Abstract
Exact Diagonalization (ED) calculations are presented for the t-J model in the presence of a uniform magnetic field. Results for 4 x 4 clusters and 2 x L ladders (L=8,10,12) with 1 and 2 holes indicate that the diamagnetic response to a perpendicular magnetic field induces a Resonating Valence Bond (RVB) state in the spin background. In the 4 x 4 square cluster, this RVB-like state competes with the zero-field AF quasi-long-range-order(QLRO): the RVB-like state is favored by higher doping and smaller values of J/t. In 2-leg ladders, the zero-field spin-liquid state is reinforced by the magnetic field: a considerable increase of rung AF correlations is observed for J/t < 0.6, for 1 and 2 holes. Pair-breaking is clearly observed in the ladders: this seems to be associated in part with changes promoted by the field in the spin correlations around the zero-fied pair.