Journal
NEW JOURNAL OF PHYSICS
Volume 22, Issue 5, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/1367-2630/ab81b6
Keywords
meta materials; non-Hermitian systems; wave amplification; non-reciprocal wave propagation; topological modes
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Funding
- National Science Foundation (NSF) through the EFRI [1741685]
- Army Research office [W911NF-18-1-0036]
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We investigate non-Hermitian elastic lattices characterized by non-local feedback interactions. In one-dimensional lattices, proportional feedback produces non-reciprocity associated with complex dispersion relations characterized by gain and loss in opposite propagation directions. For non-local controls, such non-reciprocity occurs over multiple frequency bands characterized by opposite non-reciprocal behavior. The dispersion topology is investigated with focus on winding numbers and non-Hermitian skin effect, which manifests itself through bulk modes localized at the boundaries of finite lattices. In two-dimensional lattices, non-reciprocity is associated with directional wave amplification. Moreover, the combination of skin effect in two directions produces modes that are localized at the corners of finite two-dimensional lattices. Our results describe fundamental properties of non-Hermitian elastic lattices, and suggest new possibilities for the design of meta materials with novel functionalities related to selective wave filtering, amplification and localization. The considered non-local lattices also provide a platform for the investigation of topological phases of non-Hermitian systems.
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