Gate-modulated reflectance spectroscopy for detecting excitonic states in two-dimensional semiconductors

We have developed a microspectroscopy technique for measuring gate-modulated reflectance to probe excitonic states in two-dimensional transition metal dichalcogenides. Through the use of gate-modulated spectroscopy, we were able to detect excited states of excitons and trions, which would typically have weak optical signals in traditional reflectance spectroscopy. Using a transfer matrix method for spectral analysis, the binding energy of trion 2s was determined to be 26 meV. As observing the Rydberg series of excitonic states provides fruitful information on the strong Coulomb interaction in two-dimensional systems, gate-modulated spectroscopy can be a versatile tool for understanding underlying many-body physics as well as designing next-generation quantum optoelectronics based on two-dimensional materials.