Unraveling the unique response behaviors of ultrathin transition metal dichalcogenides to external excitations

Designing novel transition metal dichalcogenides (TMDCs) are highly important for achieving superior performances in advanced optoelectrical devices of broad applications. Although many TMDCs materials have been synthesized and studied, the response behaviors of TMDCs under external excitations still lack in-depth investigations. To address this challenge, we have established a library of TMDCs including 56 types of materials and revealed their response behaviors to the external electric fields and strains as well as the possibility to drive phase transitions under the external excitations. We have explored the thermodynamic stability, band structures, electronic structures, and optical properties of these TMDCs. Under the external electric field, the gradual change of energy results in the conversion from semiconductors to metals, which enables the construction of heterojunctions while the Landau phase transitions are absent. In comparison, the external strain not only lowers the overall symmetry but also induces strong p-& pi; hybridizations to realize unique electronic properties. In particular, Dirac cones are noticed in the 1H-TcTe2 within 45-100 GPa, supporting a novel quasi heavy-fermion topological Kondo insulator induced by the phase transition under the external strains for the first time in TMDCs. This work offers fundamental knowledge to discover novel TMDCs candidates with superior optoelectrical properties.