High-Harmonic Circular Dichroism as a Probe of Topological Order in Kondo Insulators

How can we detect topological order when it is dependent on strong interactions that create new effective quasiparticle bands? Angle-resolved photoemission spectroscopy studies of topological Kondo insulator (TKI) candidates have measured surface states, but their topological versus trivial origin is debated. Chacón et al. studied circular dichroism as a probe of topological order in non-interacting systems, but it has yet to be applied to correlated topological matter. We propose circular dichroism (CD) in high-harmonic generation (HHG) as an optical probe of a TKI, overcoming the limits of direct band imaging. 

On a 3D primitive cubic lattice, we derived an auxiliary-boson mean-field Hamiltonian with k-dependent hybridization, applied a Peierls substitution, and developed a self-consistency solver to determine values of the auxiliary-boson amplitude, the constraint Lagrange multiplier, and the chemical potential. We simulate the HHG spectrum across multiple field strengths using linear polarization and dynamically calculate the Z₂ indices. 

We present the HHG spectrum simulations and Z₂ indices characterizing the topological phase. We will extend this to circular polarization to compute the current response and the CD. This will establish whether HHG-CD probes topological order under strong correlations, and if the auxiliary-boson mean-field framework captures that response.