  We theoretically investigate the effects of strain-induced pseudomagnetic
fields on the transmission probability and the ballistic conductance for Dirac
fermion transport in suspended graphene. We show that resonant tunneling
through double magnetic barriers can be tuned by strain in the suspended
region. The valley-resolved transmission peaks are apparently distinguishable
owing to the sharpness of the resonant tunneling. With the specific strain, the
resonant tunneling is completely suppressed for Dirac fermions occupying the
one valley, but the resonant tunneling exists for the other valley. The
valley-filtering effect is expected to be measurable by strain engineering. The
proposed system can be used to fabricate a graphene valley filter with the
large valley polarization almost 100%.
