Absorption-lasing effects and exceptional points in parity-time symmetric non-Hermitian metaplates

Abstract

Non-Hermitian systems that possess loss and gain have been receiving a great deal of interest in various wave problems demonstrating diverse unprecedented wave phenomena. Here, we theoretically and numerically investigate the Parity-Time (PT) symmetric metaplate with balanced loss and gain based on shunted piezoelectric layers. We present the coherent perfect absorption and lasing effects (CPAL) for flexural waves occurring in the PT broken phase via designing the circuit parameters and discuss their physical mechanisms. Moreover, we focus on the exceptional points (EP) behaving as thresholds of phase transitions and realize unidirectional reflectionless for incident waves from different directions by adjusting the circuit parameters. We further employ EP to realize unidirectional cloakings. Finally, we contrastively study the origins and sensitivities of the non-Hermitian EP and the Hermitian diabolic point (DP) for elastic waves. Our study explores complex material parameters of elastic plates and offers a reliable platform for designing the non-Hermitian elastic wave phenomena, paving the way for highly sensitive sensors, asymmetric wave control, wave absorption and amplification, and energy harvesting.