We simulate the attosecond transient absorption spectroscopy (ATAS) of monolayer hexagonal boron nitride (hBN) using the time-dependent density functional theory and the two-band density-matrix equations within the tight-binding approximation. The simulation results from the two methods are qualitatively consistent. We focus on the fishbone structure around the $\text{M}$ point, which exhibits a temporal period equal to that of the pump laser. To gain deeper insight into this structure, we simplify the two-band model to a single-electron model located at the $\mathrm{M}$ point, allowing us to derive an analytical expression that can qualitatively reproduce the numerical results. Our analytical results reveal that both the interband transition dipole moments (TDMs) and the Berry connection play important roles in the fishbone structure of the ATAS. Furthermore, by isolating the influence of the Berry connection in the ATAS, we obtain two spectra that are respectively dominated by the interband TDMs and the Berry connection. Moreover, we have also investigated the dependence of ATAS on the gap energy based on the tight-binding approximation. The results demonstrate that the ATAS intensity is enhanced as the gap energy increases, in agreement with our analytical prediction. Our study may shed light on the generation mechanism of the fishbone structure of the ATAS in hBN.

Close

PrevNext

View figure in article

• Ultrafast phenomena
• Hexagonal boron nitride
• Density functional theory
• Density matrix methods
• Transient absorption spectroscopy