Structure-controlled valley splitting and anomalous valley Hall effect in Janus VSe2/VSeX (X = S, Te) heterojunctions

Abstract

Ferrovalley materials possess spontaneous valley splitting and anomalous valley Hall effect (AVHE) characteristics, making this an ideal platform for valleytronic information devices. The efficient regulation of valley splitting and the anomalous Hall current is critical for the realization of information coding. In this work, to realize the regulation of valley properties, Janus VSe2/VSeX (X = S, Te) heterojunctions are investigated using first-principles calculations. Spontaneous valley splitting and the AVHE can be achieved in VSe2/VSeX. In addition, the asymmetrical structure, different stacking configurations of heterojunctions, and the intrinsic polarity of the Janus VSeX monolayer can regulate the band alignments, i.e. type-Ⅰ, -Ⅱ, and -Ⅲ band alignments can be realized, and they are accompanied with the switch between semiconductor and metal phases. Moreover, the structure-controlled valley states and AVHE are obtained. When altering the Janus VSeS and VSeTe, the K and K′ valleys possess contrary characteristics: opposite spin signs and valley splitting occurred. Accordingly, we design a low-power-consumption switch to achieve multistate storage without external field regulation. The results can provide an alternative avenue for spintronics and valleytronics devices.