High-order harmonic generation from topological insulators

High-order harmonic generation (HHG) has been studied extensively in gaseous media. One of the interesting applications of HHG is the use of underlying strong-field-driven electron dynamics to probe the orbital structures and dynamics in isolated small molecules. Recently, the HHG process has also been realized in solid materials, which has sparked interest in scrutinizing its prospects as a novel ultrafast probe of the solid materials in an all-optical setting [1]. The ongoing activities involve the use of underlying inter- and intra-band dynamics to probe valence charge densities in the real space and the band structure in the momentum space including topological properties. The latest theoretical results predict the possibility of probing topological phase transitions in the Haldane system using circular dichroism in HHG [2]. In this talk, I will give a brief overview of the field and present our new experimental and theoretical results on the generation of high-order harmonics from a prototypical three-dimensional topological insulator Bi₂Se₃ subjected to strong mid-infrared laser fields [3]. Our study scrutinizes HHG as a novel spectroscopic nonlinear optical probe of topological insulators. Its unique features include the unprecedented access to ultrafast dynamics occurring in the sub-cycle time scale of the driving laser field, with implications for ultrafast metrology and light-field driven electronics.
[1] “Review: High-harmonic generation from solids” Shambhu Ghimire and David Reis, Nature Physics, 15, 10-16, 2019 [2] “Circular dichroism in higher-order harmonic generation: Heralding topological phases and transitions in Chern insulators” Alexis Chacón et al., Phys. Rev. B 102, 134115 (2020) [3] “Strong-field physics in three-dimensional topological insulators” Denitsa Baykusheva et al., arXiv:2008.01265