Anisotropic magneto-optical response in topological nodal-line semimetals

We theoretically investigate the magneto-optical response in nodal-line semimetals (NLSMs), focusing on the roles of doping, spin–orbit coupling (SOC), temperature, and magnetic field. Incorporating a SOC-induced mass term Δ into the NLSM Hamiltonian, we analyze the Landau level structure and evaluate optical susceptibilities using the equation-of-motion formalism. Our results show that intraband transitions dominate the low-energy response due to their small energy scale, while interband transitions exhibit characteristic “half-peak” features resulting from Pauli blocking. The optical response (OR) is found to be highly anisotropic: χxx(Ω) shows the strongest absorption, followed by χyy(Ω) and χzz(Ω), reflecting the underlying symmetry and transition selection rules. Additionally, electron density and magnetic field shift absorption peaks to higher energies, while SOC lifts spin degeneracy and produces symmetric spectral splitting. These findings highlight the tunability and directional dependence of ORs in NLSMs, with implications for infrared and terahertz optoelectronic applications.