Bond order instabilities in a correlated two-dimensional metal
  Motivated by recent experimental evidence of charge order in the pseudogap phase of cuprates, we perform a variational analysis of charge-neutral, spin-singlet ordering in metals on the square lattice, using a wavefunction with double occupancy projected out. We examine ordering with and without time-reversal symmetry, with arbitrary wavevector and tunable form factor. Depending on parameters, we find d-wave bond density wave ordering with wavevector either parallel to the lattice generators or diagonally oriented, or a ground state which carries a time reversal-breaking pattern of spontaneous currents. 
Andrea Allais, Johannes Bauer, Subir Sachdev
cond-mat.str-el