Light-Field-Driven Non-Ohmic Current Generation by an Intense THz Pulse in a Weyl Semimetal

In recent years, coherent electrons driven by light fields have attracted significant interest in exploring novel material phases and functionalities. However, observing coherent light-field-driven electron dynamics in solids is challenging because the electrons are scattered within several tens of femtoseconds in ordinary materials, and the coherence between light and electrons is disturbed. This study presents the light-field-driven dynamics by applying a THz pulse (similar to 1 ps) to the Weyl semimetal Co3Sn2S2, which has a relatively long coherent time (several hundred femtoseconds to several picoseconds). As the electric-field intensity of the irradiating THz pulse was increased, the reflected/emitted THz wave changed from being similar to the incident THz wave to an asymmetric electric field. This asymmetric electric field emission suggests the generation of non-Ohmic direct current via coherent acceleration, and the fact that its intensity dependence is proportional to the square of the electric field suggests electronic excitation by the Landau-Zener transition, a characteristic of the light-field picture.