Unveiling electronic correlation and ferromagnetic superexchange mechanism in van der Waals crystal CrSiTe₃

The recent discovery of intrinsic ferromagnetic order in atomically thin van der Waals crystal CrXTe₃ (X=Si,Ge) stimulates intensive studies on the nature of low-dimensional magnetism. By combining advanced many-body calculations with angle-resolved photoemission spectroscopy we investigate CrSiTe₃ single crystals and unveil the pivotal role played by the strong electronic correlations at both high- and low-temperature regime. Above the Curie temperature (Tc), Coulomb repulsion (U) drives the system into a charge transfer insulating phase. In contrast, below Tc the crystal field arranges the Cr-3d orbitals such that the ferromagnetic super-exchange profits, giving rise to the bulk ferromagnetic ground state with which the electronic correlations compete. The excellent agreement between theory and experiment establishes CrSiTe₃ as a prototype low dimensional crystal with the cooperation and interplay of electronic correlation and ferromagnetism. Ref. [1] J. X. Zhang et al., Phys. Rev. Lett. 123, 047203 (2019)