Tunable and direction-dependent group velocities in topologically   protected edge states
  Topological effects continue to fascinate physicists since more than three decades. One of their main applications are high-precision measurements of the resistivity. We propose to make also use of the spatially separated edge states. It is possible to realize strongly direction-dependent group velocities. They can also be tuned over orders of magnitude so that robust delay lines and interference devices are within reach. 
G\"otz S. Uhrig
cond-mat.mes-hall quant-ph