Effects of pressure on structural, electronic, optical, and mechanical properties of ZrTe5: A density functional theory study

Completely Anisotropic Ultrafast Optical Switching and Direction‐Dependent Photocarrier Diffusion in Layered ZrTe5

“…While the overall amplitude of the absorbance is the smallest when the polarization is parallel to the a-axis (E||a), it grows as the polarization approaches the c-axis direction (E||c), agreeing with previous observations and theoretical predictions. [50,51] The anisotropic trend is also observed in Figure 1e, where the absorbance at two energy points is presented as a function of light polarization. To confirm this observation, we performed first-principles calculations of electronic band structures and corresponding polarization-dependent absorption spectra in bulk and monolayer ZrTe 5 (Figure S4, Supporting Information), both showing a similar anisotropic trend to the experimental result in Figure 1d.…”

“…It is also noteworthy that the observed anisotropic trend (the larger absorption at E||c than that measured at E||a) can be reversed in other wavelength ranges. [50,51]…”

“…Because its layers are stacked along the out-of-plane b-axis via weak van der Waals bonding (Figure 1a), its atomically thin 2D layers can be easily exfoliated. In each layer, the crystal has an anisotropic quasi-1D structure with zigzag Te−Te and tetrahedral Zr−Te chains aligned along the a-axis (Figure 1b), leading to high anisotropy of electrical, [49] optical, [50,51] vibrational, [49,50] and thermal properties. [52] For example, the in-plane carrier mobility along the a-axis is approximately twice as large as that along the perpendicular in-plane direction (c-axis).…”

“…[46] In optics, Guo et al discovered giant dichroism and birefringence from ZrTe 5 in the visible/near-IR range. [50] This fact suggests the promising potential for ultrafast applications of the strong optical anisotropy, given that ZrTe 5 has many associated advantages, such as picosecond optical response by ultrafast carrier relaxation, [53][54][55] broadband light absorption due to the narrow bandgap, [50,51] and high carrier mobility. [49] However, the ultrafast properties of the optical anisotropy in ZrTe 5 have yet been explored.…”