  Strain can tailor the band structures and properties of graphene nanoribbons
(GNRs) with the well-known emergent pseudo-magnetic fields and the
corresponding pseudo-Landau levels (pLLs). We design one type of the zigzag GNR
(ZGNR) with reverse strains, producing pseudo-magnetic fields with opposite
signs in the lower and upper half planes. Therefore, electrons propagate along
the interface as "snake states", experiencing opposite Lorentz forces as they
cross the zero field border line. By using the Landauer-Buttiker formalism
combined with the nonequilibrium Green's function method, the existence and
robustness of the reverse strain-induced snake states are further studied.
Furthermore, the realization of long-thought pure valley currents in monolayer
graphene systems is also proposed in our device.
