Frequency-dependent quantum capacitance and plasma wave in monolayer transition metal dichalcogenides

Abstract

Frequency-dependent quantum capacitance CQ of monolayer transition metal dichalcogenides (TMDs) is computed and compared to that of graphene. It is found that the frequency dependence of CQ in TMDs differs drastically from that of graphene which has a divergent point. The plasma resonance forms when the quantum capacitance is negative and has the same magnitude as the electrostatic capacitance. The calculation shows that the plasma in TMDs depends on the band-structure-limited velocity, band gap, and doping density, which can be controlled via gate biases. The plasma frequencies of TMDs are in the rage of terahertz useful for various applications.