Anomalous nonreciprocal topological networks: stronger than Chern insulators

Abstract

Robustness against disorder and defects is a pivotal advantage of topological systems, manifested by absence of electronic backscattering in the quantum Hall and spin-Hall effects, and unidirectional waveguiding in their classical analogs. Two-dimensional (2D) topological insulators, in particular, provide unprecedented opportunities in a variety of fields due to their compact planar geometries compatible with the fabrication technologies used in modern electronics and photonics. Among all 2D topological phases, Chern insulators are to date the most reliable designs due to the genuine backscattering immunity of their non-reciprocal edge modes, brought via time-reversal symmetry breaking. Yet, such resistance to fabrication tolerances is limited to fluctuations of the same order of magnitude as their band gap, limiting their resilience to small perturbations only. Here, we tackle this vexing problem by introducing the concept of anomalous non-reciprocal topological networks, that survive disorder levels with strengths arbitrarily larger than their bandgap. We explore the general conditions to obtain such unusual effect in systems made of unitary three-port scattering matrices connected by phase links, and establish the superior robustness of the anomalous edge modes over the Chern ones to phase link disorder of arbitrarily large values. We confirm experimentally the exceptional resilience of the anomalous phase, and demonstrate its operation by building an ideal anomalous topological circulator despite its arbitrary shape and large number of ports. Our results pave the way to efficient, arbitrary planar energy transport on 2D substrates for wave devices with full protection against large fabrication flaws or imperfections.

References in corpus (19)

• Photonic Floquet Topological Insulators
• Possible Realization of Directional Optical Waveguides in Photonic Crystals with Broken Time-Reversal Symmetry
• Floquet Topological Insulator in Semiconductor Quantum Wells
• Imaging topological edge states in silicon photonics
• Scheme to Achieve Silicon Topological Photonics
• Robust optical delay lines via topological protection
• Topological characterization of periodically-driven quantum systems
• Observation of phononic helical edge states in a mechanical 'topological insulator'
• A topological quantum optics interface
• Floquet Topological Insulators for Sound
• Observation of photonic anomalous Floquet Topological Insulators
• Topologically protected acoustic helical edge states and interface states in strongly coupled metamaterial ring lattices
• Optical Resonator Analog of a Two-Dimensional Topological Insulator
• Odd viscosity in chiral active fluids
• Chiral voltage propagation in a self-calibrated topolectrical Chern circuit
• Network Models of Photonic Floquet Topological Insulators
• Realization of Anomalous Floquet Insulators in Strongly-Coupled Nanophotonic Lattices
• Phase rotation symmetry and the topology of oriented scattering networks
• Topological swing in Bloch oscillations