Electrical control of the anomalous valley Hall effect in antiferrovalley bilayers

• Published in: npj quantum materials Vol. 2; no. 1
• Main Authors: Tong, Wen-Yi, Duan, Chun-Gang
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24.08.2017; Nature Publishing Group
• Subjects: 639/301/1034; 639/301/119; Access control; Bilayers; Condensed Matter Physics; Data storage; Density functional theory; Electric fields; Electric potential; Electromagnetism; Energy bands; First principles; Hall effect; Magnetic fields; Magnetism; Majority carriers; Monolayers; Physics; Physics and Astronomy; Polarity; Polarization; Power consumption; Quantum Physics; Spintronics; Structural design; Structural Materials; Surfaces and Interfaces; Thin Films; Transition metal compounds; Tuning; Two dimensional materials; Valleys; Voltage
• ISSN: 2397-4648; 2397-4648
• DOI: 10.1038/s41535-017-0051-6

In analogy to all-electric spintronics, all-electric valleytronics, i.e., valley manipulation via electric means, becomes an exciting new frontier as it may bring revolutions in the field of data storage with ultra-high speed and ultra-low power consumption. The existence of the anomalous valley Hall effect in ferrovalley materials demonstrates the possibility of electrical detection for valley polarization. However, in previously proposed valley-polarized monolayers, the anomalous valley Hall effect is controlled by external magnetic fields. Here, through elaborate structural design, we propose the antiferrovally bilayer as an ideal candidate for realizing all-electric valleytronic devices. Using the minimal k · p model, we show that the energy degeneracy between valley indexes in such system can be lifted by electric approaches. Subsequently, the anomalous valley Hall effect strongly depends on the electric field as well. Taking the bilayer VSe 2 as an example, all-electric tuning and detecting of anomalous valley Hall effect is confirmed by density-functional theory calculations, indicating that the valley information in such antiferrovalley bilayer can be reversed by an electric field perpendicular to the plane of the system and easily probed through the sign of the Hall voltage. 2D MATERIALS: Tuning the valleys First-principles calculations reveal that the anomalous valley Hall effect can be detected and tuned through an external electric field in bilayer VSe 2 . In transition-metal dichalcogenides, the local maxima or minima of the energy bands (so called valleys) are degenerate; in analogy to spintronics, manipulation of the electronic valley degree of freedom is promising for valleytronics applications. Monolayer 2H-VSe 2 has already been put forth as a ferrovalley material, capable to exhibit spontaneous valley polarization and control its polarity under external magnetic fields. Now, Wen-Yi Tong and Chun-Gang Duan report that the valley Hall effect can be present in VSe 2 bilayers without external stimuli. A perpendicular electric field enhances the accumulation of the majority carriers in the two layers in opposite directions, induces the anomalous valley Hall effect, and controls the sign of the Hall voltage. Such a way to access and control the valley information, is significant for valleytronics applications.