Sliding Ferroelectricity Induced and Switched Altermagnetism in GaSe-VPSe3-GaSe Sandwiched Heterostructure with Strong Magnetoelectric Effect

Abstract

Magnetoelectric coupling is vital for exploring fundamental science and driving the development of high-density memory and energy-efficient spintronic devices. Altermagnets, which merge the benefits of ferromagnets and antiferromagnets, pave the way for unprecedented magnetoelectric coupling effects. However, the spin splitting in altermagnets is robustly protected by spin space group symmetry, posing a significant challenge for external manipulation. Here, we propose to utilize the coupling between the layer degree of freedom and the altermagnet to achieve an altermagnetic multiferroic with strong magnetoelectric coupling. In the GaSe-VPSe3-GaSe sandwiched structure, the magnetic order can be switched between altermagnetic and conventional antiferromagnetic by controllably breaking and restoring the combined spatial inversion and time-reversal symmetry using sliding ferroelectricity. Moreover, our systematic investigation of all pathways revealed that the transition from a ferroelectric CB stacking, through an antiferroelectric CC stacking, to a ferroelectric BC stacking is the most favorable, with an energy barrier of only 50.13 meV/f.u.. More importantly, we reveal that the microscopic mechanism of the magnetic phase transition stems from the interlayer covalent bonding of Se-Se or Se-P atomic pairs at the interface. Our findings unveil a new form of magnetoelectric coupling and lay the groundwork for designing miniature information processing and multiferroic memory devices based on altermagnetism.

Figures (6)

• Figure 1: (a) The side view of bilayer GaSe crystal structures. The blue and orange balls represents Se and Ga atoms, respectively. (b) The schematic diagram of bilayer GaSe stacking. (c, d) The schematic diagram of the constructed sandwich structure from bilayer GaSe. The sandwich structure is (c) polarization upward and (d) polarization downward. The polarization direction can be manipulated by interlayer sliding. (e, f) show band structures diagram of (c, d) sandwich structures. The altermagnetic effect can also be tuned via ferroelectric switching.
• Figure 2: (a) The top and side views of monolayer GaSe. The blue and orange balls represents Se and Ga atoms, respectively. (b) Crystal structures of monolayer VPSe$_3$ from top and side views. The blue, silver, and red balls represents Se, P, and V atoms, respectively. (c, d) The top and side views of GaSe-VPSe$_3$-GaSe sandwiched structure for (c) BB stacking and (d) CB stacking. The layer spacing is marked as d$_1$ and d$_2$. (e-h) The band structures without SOC of (e) monolayer GaSe, (f) monolayer VPSe$_3$, (g) BB stacking GaSe-VPSe$_3$-GaSe, and (h) CB stacking GaSe-VPSe$_3$-GaSe. The blue line and red line (red dotted line) denote spin up and spin down bands, respectively.
• Figure 3: (a-c) Two ferroelectric transition paths of GaSe-VPSe$_3$-GaSe sandwiched structure formed (a) from AB stacking to BA stacking, (b) from CB stacking to BC stacking, and (c) from CA stacking to AC stacking by sliding sequential order. (d-f) Sliding energy barriers (d) from AB stacking to BA stacking, (e) from CB stacking to BC stacking, and (f) from CA stacking to AC stacking, respectively.
• Figure 4: (a-c) The full space of top layer lateral shifts for (a) AB stacking, (b) AA stacking, and (c) CC stacking GaSe-VPSe$_3$-GaSe sandwiched structure. (d-f) Sliding energy barrier of top layer for (d) AB stacking, (e) AA stacking, and (f) CC stacking GaSe-VPSe$_3$-GaSe sandwiched structure along (100) direction. (g-i) The full space of bottom layer lateral shifts for (g) BB stacking, (h) AB stacking, and (i) CC stacking GaSe-VPSe$_3$-GaSe sandwiched structure. (j-l) Sliding energy barrier of bottom layer for (j) BB stacking, (k) AB stacking, and (l) CC stacking GaSe-VPSe$_3$-GaSe sandwiched structure along (100) direction.
• Figure 5: The differential charge density wave function of (a) CB stacking, (b) BB stacking, (c) CC stacking, and (d) BC stacking GaSe-VPSe$_3$-GaSe sandwiched structure. Green (upper) and magenta (lower) contours represent the gain and lose electrons, respectively.