Concepts of ferrovalley material and anomalous valley Hall effect

TLDR

Valleytronics, which exploits the valley degree of freedom, offers new avenues for information storage and electronic, magnetic, and optical switching. The authors introduce ferrovalley materials as a new ferroic family that exhibits spontaneous valley polarization, analogous to ferroelectric and ferromagnetic materials. They propose that ferrovalley materials enable valley‑based nonvolatile random‑access memory and valley filters for valleytronic devices. The 2H‑VSe₂ monolayer, with coexisting spin–orbit coupling and intrinsic exchange interaction, is a room‑temperature ferrovalley material that shows chirality‑dependent optical band gaps and an anomalous valley Hall effect.

Abstract

Abstract Valleytronics rooted in the valley degree of freedom is of both theoretical and technological importance as it offers additional opportunities for information storage, as well as electronic, magnetic and optical switches. In analogy to ferroelectric materials with spontaneous charge polarization, or ferromagnetic materials with spontaneous spin polarization, here we introduce a new member of ferroic family, that is, a ferrovalley material with spontaneous valley polarization. Combining a two-band k · p model with first-principles calculations, we show that 2H-VSe 2 monolayer, where the spin–orbit coupling coexists with the intrinsic exchange interaction of transition-metal d electrons, is such a room-temperature ferrovalley material. We further predict that such system could demonstrate many distinctive properties, for example, chirality-dependent optical band gap and, more interestingly, anomalous valley Hall effect. On account of the latter, functional devices based on ferrovalley materials, such as valley-based nonvolatile random access memory and valley filter, are contemplated for valleytronic applications.