Second Harmonic Generation in van der Waals Magnetic Topological Insulator MnBi₂Te₄

MnBi₂Te₄, a newly discovered van der Waals topological magnet, has attracted great interest due to the rich interplay of topology and intrinsic magnetism present in both bulk and atomically thin flakes. Its A-type antiferromagnetic order should also lead to layer- and magnetic-state-dependent c-type optical second harmonic generation (SHG), which can arise in centrosymmetric crystals when spin ordering breaks inversion symmetry. In this talk, I will present our measurements and progress toward understanding the SHG response of MnBi₂Te₄ from pristine bulk crystal to the atomically thin limit. I will discuss steady-state and time-resolved spectroscopic results that show how the SHG depends on excitation polarization, applied magnetic field, crystal layer thickness, and sample temperature. Our results provide useful symmetry-related information for gaining further insights into this new class of two dimensional magnetic topological insulators.