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Observing Relative Homotopic Degeneracy Conversions with Circuit Metamaterials
Maopeng Wu1, Mingze Weng1, Zhonghai Chi1
1State Key Laboratory of Tribology in Advanced Equipment, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China.
Physical Review Letters
|January 19, 2024
Summary
Researchers demonstrate deterministic nodal lines (NLs) in circuit metamaterials by achieving momentum-resolved transport measurements. They observed unexpected conversions between Weyl points (WPs) and NLs, and NLs themselves, revealing new physics in condensed matter.
Area of Science:
- Condensed Matter Physics
- Metamaterials Science
- Topological Physics
Background:
- Nodal lines (NLs) are challenging to probe due to the need for bulk momentum resolution.
- Existing methods often lack the precision to deterministically control or observe NLs.
Purpose of the Study:
- To develop a method for deterministic nodal line generation and characterization.
- To investigate degeneracy conversions involving nodal lines and Weyl points (WPs).
- To explore the role of relative homotopy in these topological transitions.
Main Methods:
- Utilizing general scattering theory to selectively excite Bloch modes in circuit metamaterials.
- Employing momentum-resolved transport measurements to characterize the circuit band structure.
- Systematically demonstrating degeneracy conversions based on relative homotopy.
Main Results:
- Successfully achieved momentum-resolved characterization of circuit band structures.
- Observed the surprising conversion of two opposite-chirality Weyl points (WPs) into a nodal line (NL).
- Documented multiband anomalies in NL-to-NL conversions, explained by non-Abelian relative homotopy.
- Discussed associated physical phenomena like Fermi arcs and parallel transport of eigenstates.
Conclusions:
- The proposed circuit platform enables deterministic control and characterization of nodal lines.
- The study reveals novel topological transitions and their underlying mathematical framework (relative homotopy).
- The platform is adaptable for studying other degeneracy conversions, including those induced by spin-orbit coupling or symmetry breaking.
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