Hidden Breathing Kagome Lattice of d Orbitals in Hexagonal TMDs

A breathing Kagome lattice is formed by corner-sharing triangles of two different directions and bond strengths. With the stronger inter-site hopping, this lattice can become a higher-order topological insulator (HOTI). Experimental realizations of breathing Kagome lattices have been reported, but there have been no reports on simple natural materials with an electronic breathing Kagome lattice. Here we theoretically prove that a monolayer hexagonal transition metal dichalcogenide (h-TMD) is an electronic breathing Kagome lattice material. The trigonal prismatic structure-driven sp²-like hybrid d orbitals create an electronic breathing Kagome lattice. As the inter-site hopping is found to be stronger than the on-site hopping, the h-TMDs are HOTI on hidden breathing Kagome lattices. We also demonstrate that h-TMD nanoflakes host topologically protected corner states. Because h-TMDs are easily synthesizable and stable at ambient conditions, our findings provide an easily accessible platform for quantum physics on condensed matter systems.