Magnetic Real Chern Insulator in 2D Metal-Organic Frameworks.

Zhang, Xiaoming; He, Tingli; Liu, Ying; Dai, Xuefang; Liu, Guodong; Chen, Cong; Wu, Weikang; Zhu, Jiaojiao et al. · Nano Lett · 2023

basic_science · Level V

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Abstract

Real Chern insulators have attracted great interest, but so far, their material realization is limited to nonmagnetic crystals and systems without spin-orbit coupling. Here, we reveal the magnetic real Chern insulator (MRCI) state in a recently synthesized metal-organic framework material Co<sub>3</sub>(HITP)<sub>2</sub>. Its ground state with in-plane ferromagnetic ordering hosts a nontrivial real Chern number, enabled by the <i>C</i><sub>2<i>z</i></sub><i>T</i> symmetry and robustness against spin-orbit coupling. Distinct from previous nonmagnetic examples, the topological corner zero modes of MRCIs are spin-polarized. Furthermore, under small tensile strains, the material undergoes a topological phase transition from the MRCI to a magnetic double-Weyl semimetal phase, via a pseudospin-1 critical state. Similar physics can also be found in closely related materials Mn<sub>3</sub>(HITP)<sub>2</sub> and Fe<sub>3</sub>(HITP)<sub>2</sub>, which also exist. Possible experimental detections and implications of an emerging magnetic flat band in the system are discussed.