Interlayer excitons (ILXs) - electron-hole pairs bound across two atomically thin layered semiconductors - have emerged as attractive platforms to study exciton condensation, single-photon emission and other quantum-information applications. Yet, despite extensive optical spectroscopic investigations, critical information about their size, valley configuration and the influence of the moir\'e potential remains unknown. Here, we captured images of the time- and momentum-resolved distribution of both the electron and the hole that bind to form the ILX in a WSe2/MoS2 heterostructure. We thereby obtain a direct measurement of the interlayer exciton diameter of ~5.4 nm, comparable to the moir\'e unit-cell length of 6.1 nm. Surprisingly, this large ILX is well localized within the moir\'e cell to a region of only 1.8 nm - smaller than the size of the exciton itself. This high degree of localization of the interlayer exciton is backed by Bethe-Salpeter equation calculations and demonstrates that the ILX can be localized within small moir\'e unit cells. Unlike large moir\'e cells, these are uniform over large regions, thus allowing the formation of extended arrays of localized excitations for quantum technology.
@article{arxiv.2108.01933,
title = {Moir\'e-localized interlayer exciton wavefunctions captured by imaging its electron and hole constituents},
author = {Ouri Karni and Elyse Barré and Vivek Pareek and Johnathan D. Georgaras and Michael K. L. Man and Chakradhar Sahoo and David R. Bacon and Xing Zhu and Henrique B. Ribeiro and Aidan L. O'Beirne and Jenny Hu and Abdullah Al-Mahboob and Mohamed M. M. Abdelrasoul and Nicholas S. Chan and Arka Karmakar and Andrew J. Winchester and Bumho Kim and Kenji Watanabe and Takashi Taniguchi and Katayun Barmak and Julien Madéo and Felipe H. da Jornada and Tony F. Heinz and Keshav M. Dani},
journal= {arXiv preprint arXiv:2108.01933},
year = {2021}
}