Laser‐Induced Hole Coherence and Spatial Self‐Phase Modulation in the Anisotropic 3D Weyl Semimetal TaAs

Abstract Laser‐induced electron coherence is a fascinating topic in manipulating quantum materials. Recently, it has been shown that laser‐induced electron coherence in 2D materials can produce a third‐order nonlinear optical response spatial self‐phase modulation (SSPM), which has been used to develop a novel all‐optical switching scheme. However, such investigations have mainly focused on electron coherence, whereas laser‐induced hole coherence is rarely explored. Here, the observation of the optical Kerr effect in 3D Weyl semimetal TaAs flakes is reported. The nonlinear susceptibility (χ (3) ) is obtained, which exhibits a surprisingly high value (with = 9.9 × 10 −9 e.s.u. or 1.4 × 10 −16 m 2 V −2 at 532 nm). This cannot be explained by the conventional electron mobility, but can be well understood by the unique high anisotropic hole mobility of TaAs. The wind‐chime model and χ (3) carrier mobility correlation adequately explain the results, suggesting the crucial role of laser‐induced nonlocal ac hole coherence. These observations extend the understanding of SSPM from 2D to 3D quantum materials with anisotropic carrier mobility and from electron coherence to hole coherence.