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 of C*-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 the K-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.
Cheng, Wenting, Cerjan, Alexander Witte, Ying Chen, Ssu, Prodan, Emil, Loring, Terry A., & Prodan, Camelia (2023). Revealing topology in metals using experimental protocols inspired by K-theory. Nature Communications, 14(1). https://doi.org/10.1038/s41467-023-38862-2
Cheng, Wenting, Cerjan, Alexander Witte, Ying Chen, Ssu, et al., "Revealing topology in metals using experimental protocols inspired by K-theory," Nature Communications 14, no. 1 (2023), https://doi.org/10.1038/s41467-023-38862-2
@article{osti_2311413,
author = {Cheng, Wenting and Cerjan, Alexander Witte and Ying Chen, Ssu and Prodan, Emil and Loring, Terry A. and Prodan, Camelia},
title = {Revealing topology in metals using experimental protocols inspired by K-theory},
annote = {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 of C*-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 the K-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.},
doi = {10.1038/s41467-023-38862-2},
url = {https://www.osti.gov/biblio/2311413},
journal = {Nature Communications},
issn = {ISSN 2041-1723},
number = {1},
volume = {14},
place = {United States},
publisher = {Nature Publishing Group},
year = {2023},
month = {05}}
Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE Laboratory Directed Research and Development (LDRD) Program