Speaker
Description
Attosecond transient absorption and reflectivity spectroscopy provide direct access to electron motion in quantum materials, enabling the study of light induced phases with unprecedented temporal resolution and offering a route to elucidate the role of electron correlations in ultrafast transient phases. In many experiments, however, the spectral response is dominated by the dynamical Franz-Keldysh effect, which arises from the coherent motion of light-driven electrons. Despite its prominence, this response also contains subtle information about the underlying topological structure of the system.
Here, we present a numerical study of a Chern insulator whose topological character is controlled through second-order hopping terms. We simulate the nonequilibrium electron dynamics driven by a circularly polarized infrared pump and probed by an ultrafast attosecond x-ray pulse [1]. Our results reveal a pronounced laser-induced dichroism that provides a clear spectral signature of the topological phase. By analyzing this dichroism, we establish a direct connection between the observed spectral features and the Berry curvature distribution of the material.
These findings demonstrate that attosecond absorption spectroscopy can be leveraged to detect and characterize nontrivial topological phases. This work opens new avenues for probing quantum materials through laser-driven electron dynamics and highlights attosecond techniques as a potential tool to investigate the topological phase structure.
[1] Juan F P Mosquera et al., Rep. Prog. Phys. 87, 117901 (2024)