Microwave reflectometry of bilayer MoSe₂

Heterostructures of atomically thin transition metal dichalcogenides (TMDs) host an exotic electronic phase diagram arising from strong electron-electron interactions. However, the D.C. transport measurements that are traditionally employed to study these phases can be limited by large contact resistances in TMDs. Microwave reflectometry provides a method to measure both the real and imaginary parts of the microwave conductivity of TMDs without Ohmic contacts. The evolution of the real and imaginary parts of the conductivity as a function of carrier density can reveal information about the vibrational modes and the role of disorder in a zero-field Wigner solid. We fabricate a dual-gated, hBN encapsulated heterostructure of natural bilayer MoSe₂ in a Corbino-gate geometry, which acts as a local probe for the measurement. We then use a microwave resonator circuit to measure the AC conductivity of bilayer MoSe₂ and explore metal-insulator transitions at low doping densities and cryogenic temperatures.