Optically induced topological phase transition in two dimensional square lattice antiferromagnet

Area of Science:

• Condensed Matter Physics
• Topological Materials
• Quantum Optics

Background:

• Two-dimensional square lattice antiferromagnets with spin-orbit coupling and nonsymmorphic symmetry are identified as topological insulators (TI).
• Opto-spintronic applications require novel ways to control electronic properties with light.

Purpose of the Study:

• To theoretically investigate the Floquet states of an antiferromagnetic topological insulator under optical irradiation.
• To explore the potential for inducing topological phase transitions and creating novel electronic states.

Main Methods:

• Theoretical study of Floquet states in a driven antiferromagnetic crystal.
• Analysis of topological phase transitions induced by circularly and linearly polarized light.
• Investigation of band structures and density of states.

Main Results:

• Circularly polarized light drives a topological phase transition to a quantum anomalous Hall phase with tunable Chern numbers.
• Phase boundaries exhibit semimetallic behavior with one, two, or three band valleys.
• Linear polarization induces an effective antiferromagnetic exchange field, altering the topological phase regime.
• Near phase boundary intersections, nearly flat bulk bands lead to a high density of states.

Conclusions:

• Floquet engineering offers a pathway to control topological phases in antiferromagnetic materials.
• The observed phenomena hold promise for opto-spintronic devices.
• Tunable semimetal states and flat bands are key features for future applications.