Special CMP Seminar: “Ab Initio Predictions of the Effects of Many-Body Interactions in Low-Dimensional Materials”

25 Jul 2025
Seminars and colloquia
Time
Venue
Simpkins Lee Seminar Room
Martin Wood Complex, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU
Speaker(s)

Professor Su Ying Quek, National University of Singapore

Seminar series
CMP seminar
For more information contact

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)