  Valley degree of freedom besides spin is a promising candidate as a carrier
of information. Spintronics has come a long way and spin modulation can be
realized by quantum interference and spin-orbit coupling effect. However, the
control of valley degree of freedom using quantum interference is still a
problem to be explored. Here we discover a mechanism of producing valley
polarization in a monolayer transition metal dichalcogenides nanoribbon with
attached stubs, in which valley-resolved Fano resonance are formed due to the
quantum interference of intervalley backscattering. When the quantum
interference occurs between the localized states at the edge of the stubs and
the continuous channels in the nanoribbon, the transmission dips of Fano effect
is valley-polarized. As the number of stubs increases, the valley-polarized
transmission dips will split and valley-resolved minigaps are formed by Fano
resonance with intervalley backscattering in stub superlattice. When the
electron incident energy is in these valley-resolved gaps of the superlattice,
even with several stubs, the transmission can have a significant valley
polarization. Our finding points to an opportunity to realize valley
functionalities by quantum interference.
