Understanding coherent ultrafast charge transfer in two-dimensional van der Waals heterostructures is essential for revealing nonequilibrium processes and advancing optoelectronic device engineering. Here, we employ terahertz emission spectroscopy to probe gate-tunable coherent charge transfer (CT) in graphene/MoS2 heterostructures. Our experimental and analytical results demonstrate that the gate voltage modulates coherent CT (i.e., direct CT) by tuning the heterostructure’s built-in electric field; a higher gate voltage diminishes this field, thereby suppressing the coherent CT component. In contrast, the incoherent CT (photothermionic emission) component exhibits the opposite trend. We attribute this to a gate-induced increase in hot carriers that can overcome the interfacial barrier, an effect that dominates the concurrent reduction in the built-in field. Our findings reveal the fundamental mechanisms of gate-controlled charge dynamics, providing deeper insight into carrier transport in van der Waals heterostructures and a guideline for device development.
Wang et al. (Thu,) studied this question.