  Despite many reports of valley-related phenomena in graphene and its
multilayers, current transport experiments cannot probe valley phenomena
without the application of external fields. Here we propose a gate-defined
valley splitter as a direct transport probe for valley phenomenon in graphene
multilayers. First, we show how the device works, its magnetotransport
response, and its robustness against fabrication errors. Secondly, we present
two applications for valley splitters: (i) resonant tunneling of quantum dots
probed by a valley splitter shows the valley polarization of dot levels; (ii) a
combination of two valley splitters resolves the nature of order parameters in
mesoscopic samples.
