Photonic Z_{2} Topological Anderson Insulators

Area of Science:

• Topological physics
• Condensed matter physics
• Photonics

Background:

• Topological Anderson insulators (TAIs) are typically realized without symmetry protection.
• Chern TAIs in photonic systems exemplify this phenomenon.
• Disorder's role in inducing nontrivial topology is a recent, surprising discovery.

Purpose of the Study:

• To theoretically propose a scheme for disorder-induced symmetry-protected topological phase transitions in 2D photonic crystals.
• To utilize transverse magnetic and electric polarizations as pseudospin degrees of freedom.
• To realize a photonic Z2 TAI phase robust against pseudospin non-conservation.

Main Methods:

• Utilizing a combined time-reversal, mirror, and duality symmetry (Tf=TMzD).
• Developing a novel scattering approach to analyze topological properties.
• Employing transmission structures to observe phase trivialization.

Main Results:

• Demonstrated a disorder-induced symmetry-protected topological phase transition.
• Realized a photonic Z2 TAI phase that persists without pseudospin conservation.
• Showcased that topology in QSH and Z2 TAIs can be manifested by accumulated spin rotations of reflected waves.

Conclusions:

• Disorder can induce symmetry-protected topological phases in photonic systems.
• The proposed scheme realizes a robust photonic Z2 TAI.
• The study contrasts Z2 TAIs with Z-classified quantum spin Hall TAIs, highlighting differences in spin coupling and topological indices.