Low-frequency current fluctuations in doped ladders

Charge current static and dynamical correlations are computed by exact diagonalization methods on a two-leg ${t-t}^{\prime }-J$ ladder which exhibits a sharp transition between a Luther-Emery (LE) phase of hole pairs and a phase with deconfined holes. In the LE phase, we find short-range low-energy incommensurate current fluctuations which are intrinsically connected to the internal charge dynamics within each hole pair. When hole pairs break up, the maximum of the current susceptibility moves to the commensurate wave vector π. These results support the existence of short-range low-energy fluctuating staggered currents which extend spatially on the scale of the average hole-hole separation.