期刊
NATURE
卷 606, 期 7912, 页码 82-+出版社
NATURE PORTFOLIO
DOI: 10.1038/s41586-022-04609-0
关键词
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资金
- European Research Council (ERC) [759644-TOPP]
- European Union [732894]
- ETH Fellowship programme [20-2 FEL-66]
By combining the controlled breaking of time-reversal symmetry with non-Hermitian dynamics, researchers have imposed chirality on phononic states, leading to unique symmetries and dynamics. Through time-modulated radiation pressure forces in nano-optomechanical networks, time-reversal symmetry is broken and chiral energy flow among mechanical resonators is observed. Furthermore, introducing non-conserving squeezing interactions, they observe a non-Hermitian Aharonov-Bohm effect and phononic amplification in ring-shaped networks, opening up new possibilities for exploring non-Hermitian topological bosonic phases and applications.
Imposing chirality on a physical system engenders unconventional energy flow and responses, such as the Aharonov-Bohm effect(1) and the topological quantum Hall phase for electrons in a symmetry-breaking magnetic field. Recently, great interest has arisen in combining that principle with broken Hermiticity to explore novel topological phases and applications(2-16). Here we report phononic states with unique symmetries and dynamics that are formed when combining the controlled breaking of time-reversal symmetry with non-Hermitian dynamics. Both of these are induced through time-modulated radiation pressure forces in small nano-optomechanical networks. We observe chiral energy flow among mechanical resonators in a synthetic dimension and Aharonov-Bohm tuning of their eigenmodes. Introducing particle-non-conserving squeezing interactions, we observe a non-Hermitian Aharonov-Bohm effect in ring-shaped networks in which mechanical quasiparticles experience parametric gain. The resulting complex mode spectra indicate flux-tuning of squeezing, exceptional points, instabilities and unidirectional phononic amplification. This rich phenomenology points the way to exploring new non-Hermitian topological bosonic phases and applications in sensing and transport that exploit spatiotemporal symmetry breaking.
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