Nonlinear dynamics of topological Dirac fermions in 2D spin-orbit coupled materials

TL;DR

This paper explores the nonlinear optical responses of topological Dirac fermions in 2D spin-orbit coupled materials, revealing signatures of topological phase transitions through Kerr effect and harmonic generation, aiding in material characterization.

Contribution

It demonstrates how nonlinear optical processes can detect topological phase transitions and characterize topological invariants in graphene family materials.

Findings

Nonlinear Kerr effect reveals topological phase transition signatures.

Third-harmonic generation encodes information about Dirac cones.

Cross-polarized field components enable topological invariant detection.

Abstract

The graphene family materials are two-dimensional staggered monolayers with a gapped energy band structure due to intrinsic spin-orbit coupling. The mass gaps in these materials can be manipulated on-demand via biasing with a static electric field, an off-resonance circularly polarized laser, or an exchange interaction field, allowing the monolayer to be driven through a multitude of topological phase transitions. We investigate the dynamics of spin-orbit coupled graphene family materials to unveil topological phase transition fingerprints embedded in the nonlinear regime and show how these signatures manifest in the nonlinear Kerr effect and in third-harmonic generation processes. We show that the resonant nonlinear spectral response of topological fermions can be traced to specific Dirac cones in these materials, enabling characterization of topological invariants in any phase by detecting the cross-polarized component of the electromagnetic field. By shedding light on the unique processes involved in harmonic generation via topological phenomena our findings open an encouraging path towards the development of novel nonlinear systems based on two-dimensional semiconductors of the graphene family.