Dual-Switch Control Advances Layer-Locked Anomalous Valley Hall Effect in 2D VS2

Scientists are unlocking new potential in spintronics by exploring the interplay between ferroelectric and antiferromagnetic materials. Quan Shen, Wenhu Liao, and colleagues from Jishou University, alongside Degao Xu, Jiansheng Dong, and Jianing Tan, report a breakthrough in controlling valley polarisation within bilayer VS2, a material exhibiting both ferroelectric and antiferromagnetic properties. Their research demonstrates a ‘dual-switch’ mechanism , electrical and magnetic control of a layer-locked anomalous valley Hall effect , a significant step towards creating multifunctional devices with independently manipulable states. This work not only reveals strong magnetoelectric coupling, allowing electric and magnetic switching to modulate valley, layer, and spin, but also establishes a new operational paradigm for 2D multiferroics and paves the way for advanced multi-state memory and spin-valleytronic logic devices.

Scientists are unlocking new potential in Spintronics by exploring the interplay between ferroelectric and antiferromagnetic materials.

Bilayer VS2 enables switchable valley Hall

This breakthrough reveals a pathway to manipulate coupled spin and valley degrees of freedom, crucial for advancements in spinvalleytronics, by independently addressing these states with distinct stimuli. The research team achieved this by exploiting a system where ferroelectric and antiferromagnetic orders coexist, a configuration previously elusive in a single material. Experiments show the Berry curvature exhibits both valley-contrasting and layer-locked characteristics, directly underpinning the observed switchable Hall response. This equivalence suggests a universal mechanism for electrically switchable spin-valley phenomena in layered ferroelectric antiferromagnets with broken spatial and time-reversal symmetry.

The researchers employed Density functional theory (DFT) calculations using the VASP code, with the projector augmented-wave (PAW) method and the PBE generalized gradient approximation (GGA) to describe the exchange-correlation functional. Structural relaxations were performed until the total energy change and maximum atomic force fell below 10−6 eV and 0.001 eV/Å, respectively, utilizing a plane-wave kinetic energy cutoff of 500 eV and a vacuum region of 20 Å to prevent spurious interactions. Grimme’s DFT-D3 correction was applied to accurately account for van der Waals interactions within the bilayer system, ensuring reliable modelling of interlayer effects. The team generated bilayer configurations by sliding the top layer relative to a fixed bottom layer, fully relaxing all atomic positions and calculating the total energy of each configuration to map the energy landscape. This meticulous computational approach allowed for a detailed understanding of the interplay between ferroelectric, antiferromagnetic, and valleytronic properties in bilayer VS2, ultimately leading to the discovery of the dual-switch mechanism and its potential for future technological applications. The findings open exciting possibilities for developing novel spintronic and valleytronic devices with enhanced functionality and performance.

VS2 Bilayer Simulations Using DFT and VASP reveal

Scientists employed density functional theory (DFT) calculations using the Vienna ab initio Simulation Package (VASP) to investigate the electronic and magnetic properties of VS2 bilayers. Structural relaxations were performed until the total energy change and maximum atomic force fell below 10⁻⁶ eV and 0.001 eV/Å, respectively,0.1 meV/f. u. for interlayer sliding between ferroelectric states, confirming the ease with which the polarization can be switched. The Berry curvature exhibits both valley-contrasting and layer-locked characteristics, which underpin a switchable Hall response, a crucial element for advanced spintronic devices. Calculations established that the AA-1 and AA-2 states exhibit opposing out-of-plane ferroelectric polarizations of magnitude 0.69×10-12 C/m, exceeding previously reported values for sliding ferroelectrics like bilayer YI2 (0.26×10-12 C/m) and FeCl2 (0.41×10-12 C/m).

The researchers computed the total energies of different magnetic configurations, consistently showing the antiferromagnetic state is energetically more favorable than the ferromagnetic state, establishing a robust preference for interlayer antiferromagnetic coupling. Phonon spectrum calculations and ab initio molecular dynamics (AIMD) simulations confirmed the monolayer dynamic and thermal stability, with the total energy difference between ferromagnetic and antiferromagnetic configurations calculated as ΔE=468 meV. The optimized monolayer VS2 structure exhibits trigonal symmetry with an in-plane lattice constant of 6.47 Å, and an indirect bandgap of 0.48 eV was revealed through electronic structure analysis without spin-orbit coupling.

VS2 bilayer, electric and magnetic valley control offer

This work establishes bilayer VS2 as a two-dimensional sliding ferroelectric-antiferromagnetic material, where both interlayer sliding and magnetic reversal provide equivalent pathways for controlling the valley-layer-spin landscape. The authors acknowledge that their calculations rely on specific structural models and approximations inherent in density functional theory, potentially influencing the precise details of the observed phenomena. Future research could focus on exploring similar dual-switch mechanisms in other 2D multiferroic materials and investigating the potential for integrating these systems into functional devices. This dual-switch mechanism, capable of electrically or magnetically addressing quantum states, defines a novel paradigm for controlling entangled electronic degrees of freedom in 2D multiferroics and establishes a concrete design principle for developing next-generation multi-state non-volatile memory and reconfigurable spin-valleytronic logic devices.