1:30 PM - QT10.02.01
Twist Angle Controls Interlayer Exciton Lifetimes in van der Waals Heterostructures
Matthias Florian2,3,Junho Choi1,Alexander Steinhoff2,Daniel Erben2,Kha Tran1,Liuyang Sun1,Jiamin Quan1,Robert Claassen1,Somak Majumder4,Jennifer Hollingsworth4,Takashi Taniguchi5,Kenji Watanabe5,Keiji Ueno6,Akshay Singh7,Galan Moody8,Frank Jahnke2,Xiaoqin Li1
The University of Texas at Austin1,University of Bremen2,University of Michigan–Ann Arbor3,Los Alamos National Laboratory4,National Institute for Materials Science5,Saitama University6,Indian Institute of Science7,University of California, Santa Barbara8
Van der Waals heterostructures (vdW-HS) offer a unique material platform with rich electronic and optical properties highly tunable via a wide selection of layer composition, strain, electric gating, and doping. The twist angle between two monolayers has emerged as a unique control knob to engineer the moiré superlattice formed by periodic variations of inter-layer atomic alignment. A type-II band alignment is typically found in a transition metal dichalcogenide hetero-bilayer, leading to the formation of interlayer excitons.  Using a low-energy continuum model, we theoretically separate two leading mechanisms that influence interlayer exciton radiative lifetimes.  The shift to indirect transitions in momentum space with an increasing twist angle and the energy modulation from the moiré potential both have a significant impact on interlayer exciton lifetimes. We further predict a distinct temperature dependence of interlayer exciton lifetimes in twisted bilayers (TBLs) with different twist angles. The results are compared to time-resolved PL measurements on a series of stacked MoSe2 / WSe2 TBLs with accurately controlled twist angles. Our studies are a first step toward using the twist angle of a vdW-HS to control exciton dynamics.
 P. Rivera, J. R. Schaibley, A. M. Jones, J. S. Ross, S. Wu, G. Aivazian, P. Klement, K. Seyler, G. Clark, N. J. Ghimire, J. Yan, D. G. Mandrus, W. Yao, and X. Xu, "Observation of long-lived interlayer excitons in monolayer MoSe2–WSe2 heterostructures", Nature Communications 6, 6242 (2015)
 J. Choi, M. Florian, A. Steinhoff, D. Erben, K. Tran, L. Sun, J. Quan, R. Claassen, S. Majumder, J. A. Hollingsworth, T. Taniguchi, K. Watanabe, K. Ueno, A. Singh, G. Moody, F. Jahnke, and X. Li, "Twist Angle-Dependent Interlayer Exciton Lifetimes in van der Waals Heterostructures", Phys. Rev. Lett. 126, 047401 (2021)