Giant gate-tunable bandgap renormalization and excitonic effects in a 2-D semiconductor

Investigating the remarkable excitonic effects in two-dimensional (2-D) semiconductors and controlling their exciton binding energies can unlock the full potential of 2-D materials for future applications in photonic and optoelectronic devices. In a recent study, Zhizhan Qiu and colleagues at the interdisciplinary departments of chemistry, engineering, advanced 2-D materials, physics and materials science in Singapore, Japan and the U.S. demonstrated large excitonic effects and gate-tunable exciton binding energies in single-layer rhenium diselenide (ReSe2) on a back-gated graphene device. They used scanning tunneling spectroscopy (STS) and differential reflectance spectroscopy to measure the quasiparticle (QP) electronic and optical bandgap (Eopt) of single-layer ReSe2 to yield a large exciton binding energy of 520 meV.