Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session B59: First-Principles Simulations of Excited-State Phenomena: Excitons and Bethe-Salpeter Equation I
11:30 AM–2:30 PM,
Monday, March 6, 2023
Room: Room 301
Sponsoring
Unit:
DCOMP
Chair: Talat Rahman, University of Central Florida
Abstract: B59.00005 : Excitonic effects on nonlinear optical responses from first principles*
12:42 PM–12:54 PM
Presenter:
Yang-hao Chan
(Academia Sinica)
Authors:
Yang-hao Chan
(Academia Sinica)
Steven G Louie
(University of California, Berkeley)
Jiawei Ruan
(UC Berkeley)
We develop an efficient ab initio approach to study second harmonic generation (SHG) and shift current including electron-hole interactions, and apply it to monolayer h-BN and MoS2. We find that for these two-dimensional materials, the strongest SHG response peaks are due to large oscillator strength of the corresponding exciton states and of inter-exciton couplings. The low-energy SHG resonant with the 1s excitonic states in monolayer MoS2, however, is not strong due to the lacking of bright 2p states as intermediate states. Selection rules for inter-exciton couplings are derived using angular quantum numbers of exciton envelope functions and their momentum derivatives. A comparison of these two materials suggests that strong trigonal warping is essential for large excitonic enhancement in hexagonal materials.
*Work done in Berkeley is supported by the U. S. Department of Energy and the National Science Foundation. YHC acknowledges support by th MOST and HCHC in Taiwan.
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