Observation of Ferroelectricity in Anti-ferromagnetic Topological Heterostructures

Magnetic topological Insulators have caught huge attention for its potential to achieve dissipationless edge state. MnBi₂Te₄, the first intrinsic anti-ferromagnetic TI, has already received focus research interest recently and exhibited many novel topological behavior. Quantum Anomalous Hall effect was observed in odd-layered MnBi₂Te₄ thin flake up to 1.4 Kelvin. Even-layered 2-dimensional MnBi₂Te₄, whcih is anti-ferromagnetic axion insulator, is the perfect platform to investigate quantized topological magnetoelectric coupling and layer-locked berry curvature. Here, we report a unconventional ferroelectric behavior by stacking MnBi₂Te₄ with InBiSe₃, a trivial semiconctuor sharing a similar crystal structure as MnBi₂Te₄ with 6 percent lattice mismatch. MnBi₂Te₄ based moire heterostructure have not been reported and similar ferroelectricity has been observed in graphene-based moire systems. Combined with its magneto-electric coupling and ferromagnetic order, this multiferroic system shows potential for further exploring various topological phenomena.