Topological Magnetic-Spin Structures in Two-Dimensional Van Der Waals Cr₂Ge₂Te₆

Long-range ferromagnetic order down to atomic layers provides an important degree of freedom in engineering two-dimensional (2D) materials and their heterostructure devices for spintronics, valleytronics and magnetic tunnel junction switches. Using direct imaging by cryo-Lorentz transmission electron microscopy we report that topologically nontrivial magnetic-spin states, skyrmionic bubbles, can be realized in exfoliated insulating 2D van der Waals Cr₂Ge₂Te₆. Due to the competition between dipolar interactions and uniaxial magnetic anisotropy, hexagonally-packed nanoscale bubble lattices emerge in the ab plane by field cooling. Despite a range of topological spin textures arising due to pair formation and annihilation of Bloch lines, bubble lattices with single chirality are prevalent. Our observation of topologically-nontrivial homochiral skyrmionic bubbles in exfoliated vdW materials provides a new avenue for novel quantum states in atomically-thin insulators for magneto-electronic and quantum devices.