Universal absorption of two-dimensional materials within k ⋅ p method

Publication date: Available online 18 July 2018Source: Physics Letters AAuthor(s): Rong Huang, Jun Li, Zhenhua Wu, Wen Yang, Wei Huang, Cheng Li, Songyan ChenAbstractThe universal optical absorption is a fascinating property existing in certain two-dimensional (2D) materials. By introducing a general two-band k⋅p effective Hamiltonian, we demonstrate that the absorptance can manifest an universal value at the direct band-edge of 2D materials in three specific cases. However, for general 2D materials, the absorptance becomes nonuniversal. We investigate the dependency of absorptance on the band parameters of general 2D materials. The influences of band-anisotropy and band warping are also considered. Interestingly, we find that the coherent interband coupling and the band warping are responsible for the occurrence of the saddle-point type of Van Hove singularity, which leads to strong light-matter interactions in 2D materials.

Source: Physics Letters A - July 19, 2018 Category: Physics Source Type: research