Magnetoelectrically Controlled Valley Filter and Valley Valve in Bilayer Graphene

Abstract

In the quest for what might replace conventional electronics, the emerging field of $v\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}y\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}s$ (capitalizing on local extrema in a semiconductor's band structure for information processing) is a contender. Here the valley filter and valley valve are two key elements, and it is important to combine them in a unit. The authors present a simple, viable model for such a unit, based on bilayer graphene. Device operation is based on valley-contrasting transmission, due to the valley Zeeman effect and a band gap tunable by gate voltage, by which nearly perfect filtering and very high valve efficiency are achieved. This system could yield a reversible NAND gate, for example.