Intrinsic magnetoelectric coupling induced by the flat bands in kagome van der Waals multiferroic heterostructures

Magnetic materials with enhanced magnetoelectric couplings have been sought for decades to explore the deep correlation between spin orders and electric fields and to realize multifunctional, energy-efficient devices. Using a combination of first-principles simulations and spin superexchange theory, we predict an intrinsic nonvolatile magnetoelectric coupling in artificial multiferroic van der Waals heterostructures composed of $\mathrm{CrGeT}{\mathrm{e}}_{3}$ and breathing kagome lattice $\mathrm{N}{\mathrm{b}}_{3}\mathrm{C}{\mathrm{l}}_{8}$. Our calculations show that the interlayer spin orders can be tuned between ferromagnetic and antiferromagnetic by changing the ferroelectric phase of $\mathrm{N}{\mathrm{b}}_{3}\mathrm{C}{\mathrm{l}}_{8}$. Notably, this nonvolatile magnetoelectric coupling is robust with respect to the stacking order and layer thickness. This effect is explained by the variation in hybridization between the spin states of $\mathrm{CrGeT}{\mathrm{e}}_{3}$ and flat bands of the breathing kagome lattice $\mathrm{N}{\mathrm{b}}_{3}\mathrm{C}{\mathrm{l}}_{8}$ at two ferroelectric phases. The proposed nonvolatile magnetoelectric coupling and its mechanisms offer promise for the development of artificial two-dimensional multiferroic heterostructures for magnetoelectric applications.