Extremely light carriers in a two-dimensional Fermi surface of 1,3-DAP molecule intercalated WSe₂

Band inversion induced by spin-orbit coupling in topological semimetals typically generates light charge carriers with high Fermi velocities, which are highly desirable for low-dissipation and coherent quantum transport in topological devices. The presence of these carriers is strongly dependent on the Fermi level position in real materials. 2M-WSe₂, with its topological and van der Waals nature, serves as an ideal platform for studying quantum transport in two-dimensional systems, despite the fact that interlayer coupling suppresses the formation of light carriers. Here, we solvothermally intercalate 1,3-diaminopropane molecules into the interlayer space of 2M-WSe₂, which effectively tailors the electronic structure by eliminating interlayer coupling. Simultaneously, slight electron doping via charge transfer results in a small Fermi pocket with an extremely light effective mass, 0.04-0.06 m_e as revealed by quantum oscillation measurements. Our work proves molecular intercalation as an effective approach for engineering van der Waals topological materials to achieve tailored quantum transport properties.