Martin Wood Complex, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU
Professor Su Ying Quek, National University of Singapore
Prof Marina Filip
Abstract
Two-dimensional (2D) systems are excellent platforms to investigate exotic quantum phenomena where many-body interactions play an important role. I will present our recent efforts to investigate the role of many-body interactions on the electronic and optical properties of 2D quantum materials. We develop a formalism to predict the energies of Landau levels in 2D systems [1], and show that dynamical many-body interactions significantly enhance the Landé g-factors in the presence of charge carriers. The interaction-enhanced g-factors in good agreement with recent experiments for doped transition metal dichalcogenide (TMD) monolayers, and a valley-filling instability is predicted [2]. We also discuss the effects of many-body excitonic interactions on the non-linear optical response of layered materials. We show that the inclusion of excitonic effects is required to explain experimental data for second harmonic generation [3]. We further demonstrate that, inherent in the coherent many-body nonlinear optical response is a many-body quantum geometric term for excitons. Using first principles calculations within the GW-BSE approximation, we show numerically that these quantum geometric features can significantly enhance the non-linear optical response, especially in systems with reduced dielectric screening. If time permits, I will also present recent predictions on the excitonic properties of quantum defects in 2D materials, in the context of single photon emitters [4].
[1] F. Xuan, S.Y. Quek, Valley Zeeman Effect and Landau Levels in Two-Dimensional
Transition Metal Dichalcogenides, Physical Review Research, 2, 033256 (2020)
[2] F. Xuan, S.Y. Quek, Valley-filling instability and critical magnetic field for interactionenhanced Zeeman response in doped WSe2 monolayers, npj Computational Materials,
7, 198 (2021)
[3] F. Xuan, M. Lai, Y. Wu, S.Y. Quek, Exciton-Enhanced Spontaneous Parametric DownConversion in Two-Dimensional Crystals, Physical Review Letters, 132, 246902 (2024)
[4] N.L.Q. Cheng, K.A. Ulman, S.Y. Quek, Defect Engineering in Hexagonal Boron Nitride:
Optical Properties of Stable Defect Complexes Arising from Boron Interstitials, ACS
Applied Materials and Interfaces, 17, 24058 (2025)