Taming Waves through Non-Hermiticity: From Invisible Tunneling to Unidirectional Nonlinear Pulses

Non-Hermitian wave dynamics challenge our conventional understanding of wave propagation, revealing transport behaviors inaccessible in Hermitian systems. In this seminar, I will present a few intriguing phenomena arising from these dynamics. In the first part, I will show a counterintuitive tunneling effect at the interface of a non-Hermitian system sandwiched between two Hermitian ones. Here, the non-Hermitian skin effect creates barriers at the boundaries, yet under the right conditions, a wave can tunnel through as if the interface were invisible. This phenomenon is explored in both quantum and classical regimes, with experimental demonstrations using an active electric circuit platform. In the second part, I turn focus to nonlinear systems, addressing generation of unidirectional, narrow pulses (solitons) that propagate without distortion in active mechanical setups. I present a theoretical model for generating stable unidirectional solitons by carefully balancing nonlinearity and nonreciprocity, and show how these pulses are realized experimentally, supported by analytical results and numerical simulations.

References:

Invisible tunneling through non-Hermitian barriers in nonreciprocal lattices. Sayan Jana, Lea Sirota, Physical Review B (Letter) 111 (10), L100301, (2025).
Harnessing Nonlinearity to Tame Wave Dynamics in Nonreciprocal Active Systems, Sayan Jana et al., arXiv:2502.16216 (2025).

Speaker :  Dr. Sayan Jana

Biography: 

Dr. Sayan Jana is a Postdoctoral Researcher at the Department of Mechanical Engineering, Tel Aviv University, Israel. He obtained his PhD in Theoretical Condensed Matter Physics from the Institute of Physics, Bhubaneswar, India, in 2022. His research is interdisciplinary, integrating theoretical physics and engineering to emulate complex analogue quantum and high-energy phenomena using lab-scale platforms. One key finding includes the proposal and simulation of analogue gravitational lensing and Hawking radiation using mechanical networks. These studies provide accessible routes to investigate phenomena that are otherwise difficult to observe directly in the universe. Another major research direction focuses on non-Hermitian systems, where non-conservation of energy gives rise to intriguing dynamics and interplay with topology and nonlinearity. Realizations in active metamaterials reveal novel wave phenomena and control mechanisms, with significant potential for advanced wave manipulation and energy technologies.