Valley-Selective Klein Tunneling through a Superlattice Barrier in Graphene

$K\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}n$ $t\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}g$ is the intriguing ability of massless Dirac electrons to tunnel through potential barriers, distinguishing graphene electronics from conventional electronics. Graphene's electronic structure also features a valley degree of freedom that can be used as an information carrier. Here the authors discover a remarkable functionality that arises counterintuitively from intervalley scattering: Quantum interference of intervalley backscatterings creates a pseudospin gap in a superlattice barrier, selectively blocking transmission in one valley while permitting Klein tunneling in the other. Thus a sort of valleytronic polarizer of pseudospin current could be realized.