Enhancement of chaotic subdiffusion in disordered ladders with synthetic   gauge fields
  We study spreading wave packets in a disordered nonlinear ladder with broken time-reversal symmetry induced by synthetic gauge fields. The model describes the dynamics of interacting bosons in a disordered and driven optical ladder within a mean-field approximation. The second moment of the wave packet $m_{2} = g t^{\alpha}$ grows subdiffusively with the universal exponent $\alpha \simeq 1/3$ similar to the time-reversal case. However the prefactor $g$ is strongly modified by the field strength and shows a non-monotonic dependence. For a weak field, the prefactor increases since time-reversal enhanced backscattering is suppressed. For strong fields the spectrum of the linear wave equation reduces the localization length through the formation of gaps and narrow bands. Consequently the prefactor for the subdiffusive spreading law is suppressed. 
Xiaoquan Yu, Sergej Flach
cond-mat.dis-nn cond-mat.quant-gas nlin.CD