Habib Rostami: Theory of nonlinear spectroscopy in 2D materials
Abstract
Linear response functions are essential for classifying quantum materials' physical and chemical properties. However, there are more profound schemes in the nonlinear spectroscopies, such as the Raman effect, high-harmonic generation, and photovoltaic. In this talk, I will first introduce nonlinear optical spectroscopy. Then, I will discuss recent studies on the many-body formulation of THz nonlinear optics in graphene [1,2], highlighting the importance of a conserving theory where the self-energy and vertex correction are taken into account on the same footing. We show that the nonlinear terms are strikingly ruled by the appearance of a dominant two-photon vertex which is absent at the bare level and finite even in the weak-coupling limit. Afterward, I will discuss the importance of shear phonons in the heterostructure of two-dimensional (2D) materials and explain a recent work [3] on the light-induced displacive Raman force and its application to staking manipulation in van der Waals 2D materials. Finally, I will briefly talk about a current project on the characteristics of the nonlinear spin Hall effect in 2D WTe2 [4].
[1] H. Rostami and E. Cappelluti, npj 2D Materials and Applications 5, Article number: 50 (2021).
[2] H. Rostami and E. Cappelluti, Phys. Rev. B 103, 125415 (2021).
[3] H. Rostami, arXiv:2204.08060 (2022)
[4] P. Bhalla and H. Rostami, manuscript in preparation.
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