Giant enhancement of the thermal Hall conductivity \kappa_{xy} in the   superconductor YBa_2Cu_3O_7
  In high-purity crystals of YBa_2Cu_3O_7, the quasiparticle (qp) lifetime   \tau and the (weak-field) thermal Hall conductivity \kappa_{xy} undergo dramatic increases below 90K. We present a detailed picture of the behavior of \kappa_{xy} at low temperature, in particular its scaling properties, which are directly relevant to the issue of whether Landau quantization of the qp states occurs. 
Y. Zhang, N. P. Ong, P. W. Anderson (Princeton University), D. A.   Bonn, R. Liang, and W. N. Hardy (University of British C...