Emergent Relativistic Effects in Condensed Matter
From Fundamental Aspects to Electronic Functionality

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01.05.2020

Twist-tailoring Coulomb correlations in van der Waals homobilayers


P. Merkl, F. Mooshammer, S. Brem, A. Girnghuber, K.-Q. Lin, L. Weigl, M. Liebich, C.-K. Yong, R. Gillen, J. Maultzsch, J. M. Lupton, E. Malic, R. Huber

Nature Communications

The 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.

https://www.nature.com/articles/s41467-020-16069-z
https://www.uni-regensburg.de/pressearchiv/pressemitteilung/1065200.html

 

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