Authors: Philipp Merkl, Fabian Mooshammer, Samuel Brem, Anna Girnghuber, Kai-Qiang Lin, Leonard Weigl, Marlene Liebich, Chaw-Keong Yong, Roland Gillen, Janina Maultzsch, John M. Lupton, Ermin Malic, Rupert Huber
Published: 2020-05-01
DOI: 10.1038/s41467-020-16069-z
Source: Full article
AbstractThe 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.