Broken time-reversal symmetry in strongly correlated ladder structures
  We provide, for the first time, in a doped strongly correlated system (two-leg ladder), a controlled theoretical demonstration of the existence of a state in which long-range ordered orbital currents are arranged in a staggered pattern,coexisting with a charge density wave. The method used is the highly accurate density matrix renormalization group technique.This brings us closer to recent proposals that this order is realized in the enigmatic pseudogap phase of the cuprate high temperature superconductors. 
U.Schollwoeck, Sudip Chakravarty, J. O. Fjaerestad, J. B. Marston, M.   Troyer