Strain-Tunable Spin Filtering and Valley Splitting Coexisting with Anomalous Hall Effect in 2D Half-Metallic VSe2/VN Heterostructure: Toward a Unified Spintronic-Valleytronic Platform

TL;DR

This work identifies VSe$_2$/VN as a dynamically stable, strain-tunable van der Waals heterostructure that simultaneously enables robust valley splitting and strong spin selectivity. Using first-principles calculations, the authors demonstrate a stable AA-stacked configuration with interlayer charge transfer and a work-function alignment that stabilizes the interface. The heterostructure exhibits a small PBE-indirect gap and a half-metallic tendency by HSE06, with sizable conduction-band valley splitting and a large Berry-curvature–driven anomalous Hall response; strain modulates the spin-filtering efficiency up to $82.5 ext{%}$ while tuning the Curie temperature. Collectively, these results position VSe$_2$/VN as a practical, strain-engineered platform for integrated spintronic–valleytronic devices and for exploring valley-contrasting transport phenomena.

Abstract

Rapid progress in valleytronics and spintronics is limited by the scarcity of two-dimensional materials that simultaneously provide robust valley splitting and strong spin selectivity. Here we showed that a van der Waals heterostructure (VSe2/VN) built from hexagonal VSe2 and hexagonal VN addressed this gap. Using first-principles density functional theory, phonon, ab initio molecular dynamics stability tests, Bader charge analysis, and Wannier-based Berry-curvature calculations, we demonstrated an energetically and dynamically stable heterostructure that exhibited interlayer charge transfer and a work function intermediate between the constituent monolayers. The electronic structure showed small indirect PBE gap (108.9 meV), with HSE06 indicating a half-metallic tendency; a sizable conduction-band valley splitting (ΔCKK' = 22.9 meV for spin-up and ΔCKK' = 61.3 meV for spin-down); and pronounced spin asymmetry, where the spin-down channel showed a wide semiconducting gap (0.64 eV) while the spin-up channel was nearly gapless. These features yielded a high zero-strain spin-filter efficiency P = 75.4%, tunable to 82.5% under +4% biaxial tensile strain. The heterostructure also supported non-zero, valley-contrasting Berry curvature, and a large anomalous Hall conductivity (peak sigmaxy = 568.33 S/cm). Importantly, mean-field estimation placed the ferromagnetic Curie temperature near room temperature at zero strain (Tc = 284.04 K), while Tc decreased to 183.9 K at +4% strain, the magnetic order remained robust to cryogenic temperatures, providing a beneficial tuning knob to balance spin-filter performance with thermal stability in device-relevant regimes. These results identified VSe2/VN as a practical, strain-tunable platform for integrated valleytronic, spintronic devices, and for exploring anomalous Hall and valley-dependent transport phenomena.

Figures (11)

• Figure 1: (a) Side view of pristine hexagonal VSe$_2$ monolayer. (b) Top view of pristine hexagonal VSe$_2$ monolayer. (c) Spin-polarized band structure (without SOC) of pristine hexagonal VSe$_2$ monolayer. (d) PDOS of $\textnormal{s}$, $\textnormal{p}$ and $\textnormal{d}$ orbitals of the V atom. (e) PDOS of $\textnormal{s}$, $\textnormal{p}$ orbitals of the Se atom. (f) Side view of pristine hexagonal VN monolayer. (g) Top view of pristine hexagonal VN monolayer. (h) Spin-polarized band structure (without SOC) of pristine hexagonal VN monolayer. (i) PDOS of $\textnormal{s}$, $\textnormal{p}$ and $\textnormal{d}$ orbitals of the V atom. (j) PDOS of $\textnormal{s}$, $\textnormal{p}$ orbitals of the N atom. The red line and red arrow represent the spin-up channel, while the blue line and blue arrow represent the spin-down channel.
• Figure 2: Different stackings of VSe$_2$/VN ($2 \times 2 \times 1$ supercell) heterostructure. First row indicates the top views and second row indicates the side views of the heterostructure with varying interlayer distance (D).
• Figure 3: (a) Phonon dispersion diagram of the VSe$_2$/VN heterostructure showing the absence of any imaginary frequencies, confirming its dynamic stability. (b) Variation of total energy and temperature of the VSe$_2$/VN heterostructure under the NVT ensemble at 373 K, recorded from 0 to 5 ps with a timestep of 1 fs. (c) Optimized atomic structure of the VSe$_2$/VN heterostructure. (d) Work function along with CDD diagram (with isosurface value of $0.0033~\mathrm{e}\,\AA^{-3}$) of the VSe$_2$/VN heterostructure with respect to z-axis, where the dashed line represents the vacuum level and the dotted line denotes the Fermi level. Cyan and yellow represent electron depletion and accumulation, respectively.
• Figure 4: (a) Band structure (with SOC) of unit cell VSe$_2$/VN heterostructure. Green line indicates band structure with HSE06 functional and orange line indicates band structure with PBE functional. (b) Band structure (with SOC) ($2 \times 2 \times 1$ supercell) of VSe$_2$/VN heterostructure. The color map indicates expectation values of the spin operator on the spinor wave-functions ranging from -0.50 (blue) to +0.50 (red). (c) Spin-polarized DOS ($2 \times 2 \times 1$ supercell) of VSe$_2$/VN heterostructure. Blue arrow, red arrow indicate spin-down channel and spin-up channel, respectively. The purple box shows the forbidden energy window (0.64 eV) of spin-down channel in (b) and (c).
• Figure 5: Schematic of a spin-filter using the VSe$_2$/VN ($2 \times 2 \times 1$ supercell) heterostructure. By applying external perturbation, spin-up electrons will be available for a certain energy window at the right contact.