Optimal rectification by strongly coupled spins
  We study heat transport in a pair of strongly coupled spins. In particular, we present a condition for optimal rectification, i.e., flow of heat in one direction and complete isolation in the opposite direction. We show that the strong-coupling formalism is necessary for correctly describing heat flow in a wide range of parameters, including moderate to low couplings. We present a situation in which the strong-coupling formalism predicts optimal rectification whereas the phenomenological approach predicts no heat flow in any direction, for the same parameter values. 
T. Werlang, M. A. Marchiori, M. F. Cornelio, D. Valente
quant-ph cond-mat.mes-hall cond-mat.stat-mech