Electrical control of the anomalous valley Hall effect in antiferrovalley bilayers

Abstract

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.

Valleytronics in thermoelectric materials

“…[25][26][27] Recent study shows that twodimensional effect with enhanced Seebeck coefficient has been realized under high vertical electrical field in oxide TE materials. 124 The introduction of magnetic nano-particles in TE materials also favors the zT, indicating that the inner built magnetic field would help manipulate the electron transport to obtain higher TE performance.…”

“…1). 26,27 Here, this concept is extended to the TE field to include strategies for zT enhancement concerning the modification of valley structures, which is the main aim of this review. There are three valley parameters that allow for modification (seen in Fig.…”

“…24,25 This idea, similar to spintronics, was initially applied to construct new quantum computation devices, which tune the valley polarization to store and carry information. 26,27 Subsequent applications of this concept include designing new optoelectronic devices and ferrovalley materials (Fig. 1).…”

Electrically induced 2D half-metallic antiferromagnets and spin field effect transistors

“…2D materials | 2D magnetism | half metallicity | spin field effect transistor | antiferromagnetic spintronics S caling down of spintronic devices requires the precise knowledge and delicate control of magnetic properties of materials in reduced dimensions. Two-dimensional magnetic van der Waals (vdW) crystals (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), owing to their high crystallinity and atomic thinness and flatness, innately eliminate the challenges associated with the conventional thin-film preparation process, in which extrinsic defect or surface states and spurious magnetic anisotropies would be otherwise inevitable. Our recent experimental discovery of intrinsic ferromagnetism in 2D vdW crystals revealed the prominent dimensionality effect and the unusual magnetic field effect in the emerging magnetic properties of clean 2D vdW ferromagnets (3).…”

“…Recently, a new type of single-layer ferromagnetic semiconductor in transition-metal dichalcogenides 2H-VX 2 (X = S, Se, and Te) has attracted great attention (29,30). For bilayer 2H-VSe 2 , the intralayer is still ferromagnetic, while the interlayer magnetic coupling is found to be antiferromagnetic (8,30); i.e., bilayer 2H-VSe 2 is an A-type antiferromagnetic semiconductor. In the following, we use bilayer 2H-VSe 2 as an example to demonstrate the formation of the half metallicity induced by the cross-layer electric field.…”