It is well known that when the scale of matter changes from a three-dimensional bulk to a two-dimensional, or even a single atomic layer, it often exhibits novel physical properties. According to the engineers of Giant Nano Group, two-dimensional semiconductor materials, especially two-dimensional transition metal sulfides, the two-dimensional transition metal sulfides provided by Giant Nano low-dimensional materials online are popular because they have many different characteristics from their bulk forms. The favor of scientists, for example, with the reduction of the number of layers, the two-dimensional transition metal sulfides, which were originally indirect band gap semiconductors, "turned into direct band gap semiconductors". Monolayer MoS2 with a honeycomb lattice structure and broken spatial symmetry makes it a hot material for valleytronics. These superior properties open a new chapter in the research of 2D transition metal dichalcogenides in optoelectronics and electronic devices. Based on the latest progress in electric field regulation of two-dimensional transition metal sulfides, Liu Zheng's research group from Nanyang Technological University, Singapore, has summarized them in detail from three aspects: optical properties, metal-insulator phase transition and energy valley performance regulation.

       From the perspective of optical performance regulation, theoretical calculations have demonstrated that with a specific electric field, bilayer molybdenum disulfide can achieve the transition from a direct bandgap semiconductor to an indirect bandgap semiconductor, resulting in changes in its corresponding luminescence and exciton properties. The electron concentration inside the monolayer molybdenum disulfide is changed by the electric field, which can make the luminescence spectrum of the material switch between electrically neutral excitons and charged excitons, and change the exciton binding energy. Combined with the regulation of frequency doubling of two-dimensional materials in the field of nonlinear optical properties by an external electric field, the application of two-dimensional transition metal sulfides in optoelectronic devices has been imminent.
       In terms of electrical performance regulation, by increasing the carrier concentration of two-dimensional transition metal sulfides such as molybdenum disulfide, the transition from semiconductor to metal can be achieved, and it has even been found that it exhibits superconducting properties at low temperatures. Using the two-dimensional strongly correlated system, it has also become possible to modulate the transition temperature of two-dimensional superconducting materials with an electric field. In the TiSe2 system, the electric field regulation suppresses the charge density wave (CDW) state, and at the same time makes the system exhibit a superconducting state, which provides a new idea for the study of electric field regulation of many-body states.
       The most anticipated is the performance of two-dimensional transition metal sulfides in the regulation of energy valley performance. The double-layer molybdenum disulfide can use its own structural characteristics to achieve symmetry breaking and further control the valley polarization under the action of an external electric field. Using this phenomenon, the electric field regulation of the material valley Hall effect can also be realized, which indicates the possibility of fabricating valley devices. In addition, on the surface of bulk WSe2, the electric field can also induce symmetry breaking to generate and modulate spin or valley currents. Under the modulation of a strong electric field, the energy valley properties of two-dimensional transition metal sulfides can be used to generate electro-circularly polarized light. These qualities make a big step forward in the emerging field of research in Nogani electronics. With the in-depth research on the performance regulation of two-dimensional transition metal sulfides, based on the electric field effect, combining and optimizing the optical, electrical and energy valley properties of the material, it is believed that the design and application of novel two-dimensional optoelectronic devices can be just around the corner. A fresh and splendid flower blooms in the field of technology.