Observation of Non-Hermitian Skin Effect in Thermal Diffusion

TL;DR

This paper demonstrates the non-Hermitian skin effect in thermal diffusion systems using a specially designed lattice model, revealing new topological phenomena in heat transfer with potential applications in thermal sensing and heat management.

Contribution

It is the first explicit demonstration of the non-Hermitian skin effect in diffusive thermal systems, expanding non-Hermitian physics into thermal diffusion.

Findings

Observation of transient thermal skin effect on boundaries

Experimental verification of NHSE robustness against defects

Design of a thermal diffusion lattice based on a modified SSH model

Abstract

The paradigm shift of the Hermitian systems into the non-Hermitian regime profoundly modifies the inherent topological property, leading to various unprecedented effects such as the non-Hermitian skin effect (NHSE). In the past decade, the NHSE effect has been demonstrated in quantum, optical and acoustic systems. Besides in those non-Hermitian wave systems, the NHSE in diffusive systems has not yet been explicitly demonstrated, despite recent abundant advances in the study of topological thermal diffusion. Here we first design a thermal diffusion lattice based on a modified Su-Schrieffer-Heeger model which enables the observation of diffusive NHSE. In the proposed model, the periodic heat exchange rate among adjacent unit cells and the asymmetric temperature field coupling inside unit cells can be judiciously realized by appropriate configurations of structural parameters of unit cells. The transient concentration feature of temperature field on the boundary regardless of initial excitation conditions can be clearly observed, indicating the occurrence of transient thermal skin effect. Nonetheless, we experimentally demonstrated the NHSE and verified the remarkable robustness against various defects. Our work provides a platform for exploration of non-Hermitian physics in the diffusive systems, which has important applications in efficient heat collection, highly sensitive thermal sensing and others.