All-strain based valley filter in graphene nanoribbons using snake   states
  A pseudo-magnetic field kink can be realized along a graphene nanoribbon using strain engineering. Electron transport along this kink is governed by snake states that are characterized by a single propagation direction. Those pseudo-magnetic fields point towards opposite directions in the K and K' valleys, leading to valley polarized snake states. In a graphene nanoribbon with armchair edges this effect results in a valley filter that is based only on strain engineering. We discuss how to maximize this valley filtering by adjusting the parameters that define the stress distribution along the graphene ribbon. 
L. S. Cavalcante, A. Chaves, D. R. da Costa, G. A. Farias, and F. M.   Peeters
cond-mat.mes-hall