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arXiv · 2210.03960

Theory of Optical Activity in Doped Systems with Application to Twisted Bilayer Graphene

K. Chang·Z. Zheng·J. E. Sipe·J. L. Cheng
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Abstract

We theoretically study the optical activity in a doped system and derive the optical activity tensor from a light wavevector-dependent linear optical conductivity. Although the light-matter interaction is introduced through the velocity gauge from a minimal coupling Hamiltonian, we find that the well-known ``false divergences'' problem can be avoided in practice if the electronic states are described by a finite band effective Hamiltonian, such as a few-band tight-binding model. The expression we obtain for the optical activity tensor is in good numerical agreement with a recent theory derived for an undoped topologically trivial gapped system. We apply our theory to the optical activity of a gated twisted bilayer graphene, with a detailed discussion of the dependence of the results on twist angle, chemical potential, gate voltage, and location of rotation center forming the twisted bilayer graphene.

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K. Chang, Z. Zheng, J. E. Sipe, J. L. Cheng. 2022-10-08. Theory of Optical Activity in Doped Systems with Application to Twisted Bilayer Graphene. https://doi.org/10.1103/physrevb.106.245405

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