Merkl, PhilippPhilippMerklMooshammer, FabianFabianMooshammerBrem, SamuelSamuelBremGirnghuber, AnnaAnnaGirnghuberLin, Kai-QiangKai-QiangLinWeigl, LeonardLeonardWeiglLiebich, MarleneMarleneLiebichCHAW-KEONG YONGGillen, RolandRolandGillenMaultzsch, JaninaJaninaMaultzschLupton, John MJohn MLuptonMalic, ErminErminMalicHuber, RupertRupertHuber2024-07-102024-07-102020-05-012041-1723https://scholars.lib.ntu.edu.tw/handle/123456789/719718The recent discovery of artificial phase transitions induced by stacking monolayer materials at magic twist angles represents a paradigm shift for solid state physics. Twist-induced changes of the single-particle band structure have been studied extensively, yet a precise understanding of the underlying Coulomb correlations has remained challenging. Here we reveal in experiment and theory, how the twist angle alone affects the Coulomb-induced internal structure and mutual interactions of excitons. In homobilayers of WSe2, we trace the internal 1s-2p resonance of excitons with phase-locked mid-infrared pulses as a function of the twist angle. Remarkably, the exciton binding energy is renormalized by up to a factor of two, their lifetime exhibits an enhancement by more than an order of magnitude, and the exciton-exciton interaction is widely tunable. Our work opens the possibility of tailoring quasiparticles in search of unexplored phases of matter in a broad range of van der Waals heterostructures.enINDIRECT INTERLAYER EXCITONS; BANDGAP RENORMALIZATION; MOMENTUM; VALLEY; SPIN[SDGs]SDG7journal article10.1038/s41467-020-16069-z323585152-s2.0-85084114640WOS:000531425900009https://api.elsevier.com/content/abstract/scopus_id/85084114640