RT Journal Article SR Electronic T1 Giant gate-tunable bandgap renormalization and excitonic effects in a 2D semiconductor JF Science Advances JO Sci Adv FD American Association for the Advancement of Science SP eaaw2347 DO 10.1126/sciadv.aaw2347 VO 5 IS 7 A1 Qiu, Zhizhan A1 Trushin, Maxim A1 Fang, Hanyan A1 Verzhbitskiy, Ivan A1 Gao, Shiyuan A1 Laksono, Evan A1 Yang, Ming A1 Lyu, Pin A1 Li, Jing A1 Su, Jie A1 Telychko, Mykola A1 Watanabe, Kenji A1 Taniguchi, Takashi A1 Wu, Jishan A1 Neto, A. H. Castro A1 Yang, Li A1 Eda, Goki A1 Adam, Shaffique A1 Lu, Jiong YR 2019 UL http://advances.sciencemag.org/content/5/7/eaaw2347.abstract AB Understanding the remarkable excitonic effects and controlling the exciton binding energies in two-dimensional (2D) semiconductors are crucial in unlocking their full potential for use in future photonic and optoelectronic devices. Here, we demonstrate large excitonic effects and gate-tunable exciton binding energies in single-layer rhenium diselenide (ReSe2) on a back-gated graphene device. We used scanning tunneling spectroscopy and differential reflectance spectroscopy to measure the quasiparticle electronic and optical bandgap of single-layer ReSe2, respectively, yielding a large exciton binding energy of 520 meV. Further, we achieved continuous tuning of the electronic bandgap and exciton binding energy of monolayer ReSe2 by hundreds of milli–electron volts through electrostatic gating, attributed to tunable Coulomb interactions arising from the gate-controlled free carriers in graphene. Our findings open a new avenue for controlling the bandgap renormalization and exciton binding energies in 2D semiconductors for a wide range of technological applications.