Altermagnetoelectric Spin Field Effect Transistor

Abstract

Spin field-effect transistors (SFETs) are promising candidates for low-power spin-based electronics, yet existing realizations that rely on spin-orbit coupling are constrained by limited material choices and short spin-coherence lengths. Here we propose a different operating principle based on multiferroic altermagnets, in which spin splitting is tuned by an electric field through symmetry control rather than conventional spin-orbit physics. Using an effective model combined with quantum transport simulations, we show that the conductance is determined by the degree of matching between the electrically controlled spin texture of the channel and the fixed spin polarization of ferromagnetic contacts, enabling clear ON and OFF states. Remarkably, we also address a long-standing challenge in multiferroic device design: spintronic channels require metallic carriers, whereas ferroelectricity is usually suppressed in metals. We resolve this conflict by imprinting multiferroic altermagnetism into highly conductive materials via the proximity effect. First-principles calculations for graphene on multiferroic vanadium sulfide halides confirm that graphene acquires a ferroelectrically switchable spin splitting while retaining its metallic character. These results establish a practical route to SFET implementation and identify multiferroic altermagnets as a versatile platform for next-generation spintronic devices.

Figures (4)

• Figure 1: (a) AMSFET schematic. (b) Hysteretic switching of ferroelectric polarization $\bf P$ in AFE (red) and FE (blue) transitions by electric field $\varepsilon$. (c) Schematic configurations of $\bf P$ (ellipses labeled with +/-) and spin polarization $\bf {P_s}$ (red and blue arrows), along with the corresponding illustrative momentum-dependent band structures for the FEAFM and AFEAM states. The gray dashed lines in the bands represent the determined Fermi level, $E_F$. (d) Operational principle for FEAFM with high conductance ($G$) and AFEAM with low $G$. The black, red, and blue circles represent the degenerate, spin-up, and spin-down channels, respectively. (e) and (f) Same as (c) and (d) but for FEAM-FE$^\prime$AM transition.
• Figure 2: (a) Schematic illustration of 2D rectangular magnetic sublattices $A$ (red) and $B$ (blue) with nested AFM lattice. The gray shadow represents the unit cell, the yellow and green shadows represent the [11] and [10] orientations of the calculated nanoribbon model. (b) First Brillouin zone with high symmetry points. (c) Spin-resolved band structures for FEAFM and (d) AFEAM state calculated from TB model. The gray section represents the energy region for calculating conductance ($G$). (e) Spin-dependent $G$ as a function of energy calculated along [10] and (f) [11] direction for FEAFM and AFEAM states, respectively. (g) Total $G$ of the AMSFET device with two leads. The inset illustrates the corresponding spin configuration and lattice orientation.
• Figure 3: (a) Spin-resolved band structures for FEAM and (b) FE$^\prime$AM state calculated from TB model. (c) Spin-dependent conductance as a function of energy calculated along [11] direction for FEAM and FE$^\prime$AM states, respectively. (d) Total $G$ of the AMSFET device with leads. The inset illustrates the corresponding spin configuration and lattice orientation.
• Figure 4: (a) and (b) Crystal structure of graphene/VSI$_2$ heterostructure in opposite ferroelectric (FE) phases. Red and blue polyhedra represent the two opposite spin sublattices, while the spin densities induced in graphene are highlighted in red and green, the isosurface value is $3 \times 10^{-5}$ e/bohr$^3$. (c) and (d) Corresponding calculated band structures, where black, red, and blue lines denote spin-degenerate, spin-up, and spin-down bands, respectively. Inset: band structure near the Dirac point of the graphene component.