Simulating Exceptional Non-Hermitian Metals with Single-Photon Interferometry

Area of Science:

• Condensed Matter Physics
• Quantum Physics
• Photonic Systems

Background:

• Non-Hermitian (NH) systems exhibit unique topological properties distinct from Hermitian systems.
• Nodal band structures and their topological features are crucial for understanding material properties.
• Exceptional lines (ELs) are the non-Hermitian analogs of nodal lines.

Purpose of the Study:

• To experimentally simulate and characterize non-Hermitian (NH) metals in a photonic setting.
• To investigate the topological properties of exceptional lines (ELs) in both 2D and 3D NH systems.
• To differentiate between symmetry-protected and symmetry-independent topological ELs and their behavior under perturbations.

Main Methods:

• Utilizing a photonic simulation to implement nonunitary time evolution in reciprocal space.
• Employing interferometric measurements to probe complex eigenenergies of NH Bloch Hamiltonians.
• Analyzing the impact of symmetry-breaking perturbations on the topology of ELs.

Main Results:

• Experimental simulation of NH metals with topological nodal band structures.
• Detailed study of the topology of exceptional lines (ELs) in 2D and 3D systems.
• Observation of distinct behaviors of symmetry-protected (2D) and symmetry-independent (3D) topological ELs under perturbations.

Conclusions:

• The study successfully demonstrates the experimental simulation of NH metals and their topological features in photonics.
• Distinctions between different types of topological ELs in NH systems were experimentally observed.
• The findings provide insights into the robustness and characteristics of topological phases in non-Hermitian systems.