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 in real materials strongly depends on the Fermi-level position. 2M-WSe_2, 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. In this study, we solvothermally intercalate 1,3-diaminopropane molecules into the interlayer space of 2M-WSe_2; these molecules effectively adapt to 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_\rm e, as revealed by quantum oscillation measurements. This study demonstrates that molecular intercalation is an effective approach for engineering van der Waals topological materials to achieve specific quantum transport properties.