Electronic and optical properties of alternating-twist tetralayer graphene under twist angle, interlayer bias, and sliding geometries

We theoretically analyze the energy and optical absorption spectra of alternating-twist tetralayer graphene (AT4G) under a perpendicular electric field. At larger twist angles (3°–5°), we study the effects of interlayer bias on the low-energy band structure and confirm that our perturbative analysis aligns well with the numerical results. Additionally, we observe that the optical absorption spectrum of AT4G reveals a steplike feature in its longitudinal conductivity, resulting from the splitting of Dirac nodes under the applied electric field [1]. At the magic angle (1.75°), we investigate the dependence of the interlayer AA, AB, and SP sliding geometries of the middle interface on the electronic structure of AT4G, focusing on bandwidths, band gaps, and valley Chern numbers as a function of twist angle and interlayer potential difference. Furthermore, we analyze the linear longitudinal optical absorption and the influence of the Hartree potential across various band filling factors for these sliding configurations [2].