Vibrational Effects in X-ray Absorption Spectra of Two-Dimensional Layered Materials

With the examples of the C K-edge in graphite and the B K-edge in hexagonal boron nitride, we demonstrate the impact of vibrational coupling and lattice distortions on the X-ray absorption near-edge structure (XANES) in two-dimensional layered materials. Theoretical XANES spectra are obtained by solving the Bethe–Salpeter equation of many-body perturbation theory, including excitonic effects through the correlated motion of the core hole and excited electron. We show that accounting for zero-point motion is important for the interpretation and understanding of the measured X-ray absorption fine structure in both materials, in particular for describing the σ*-peak structure.Funding agencies: Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Knut and Alice Wallenbergs Foundation; Swedish Energy Research [43606-1]; Carl Trygger Foundation [CTS16:303, CTS14:310]; JSPS KA