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Abstract Topological metals are conducting materials with gapless band structures and nontrivial edge-localized resonances. Their discovery has proven elusive because traditional topological classification methods require band gaps to define topological robustness. Inspired by recent theoretical developments that leverage techniques from the field ofC∗-algebras to identify topological metals, here, we directly observe topological phenomena in gapless acoustic crystals and realize a general experimental technique to demonstrate their topology. Specifically, we not only observe robust boundary-localized states in a topological acoustic metal, but also re-interpret a composite operator—mathematically derived from theK-theory of the problem—as a new Hamiltonian whose physical implementation allows us to directly observe a topological spectral flow and measure the topological invariants. Our observations and experimental protocols may offer insights for discovering topological behaviour across a wide array of artificial and natural materials that lack bulk band gaps.
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This content will become publicly available on July 8, 2026
Enhancing energy predictions in multi-atom systems with multiscale topological learning
The multiscale topological learning framework, based on persistent topological Laplacians, captures complex interactions and enhances energy prediction accuracy in multi-atom systems.
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- Award ID(s):
- 2052983
- PAR ID:
- 10616135
- Publisher / Repository:
- Journal of Materials Chemistry A
- Date Published:
- Journal Name:
- Journal of Materials Chemistry A
- Volume:
- 13
- Issue:
- 27
- ISSN:
- 2050-7488
- Page Range / eLocation ID:
- 21555 to 21563
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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