Observing parity-time symmetry in diffusive systems

TL;DR

This paper demonstrates the realization of PT-symmetry in diffusive systems, enabling control over thermal phase oscillations and revealing phase transition phenomena, with potential applications in heat transfer and wave propagation.

Contribution

It introduces a method to achieve PT-symmetry in diffusive systems, overcoming previous limitations in phase control and demonstrating phase transition behavior.

Findings

Complete suppression of thermal phase oscillation in PT-symmetric diffusive systems

Observation of phase transition of PT symmetry breaking

Real coupling established via thermal metamaterials

Abstract

Phase modulation has scarcely been mentioned in diffusive systems since the diffusion process does not carry momentum like waves. Recently, the non-Hermitian physics provides a new perspective for understanding diffusion and shows prospects in the phase regulation of heat flow, for example, the discovery of anti-parity-time (APT) symmetry in diffusive systems. The precise control of thermal phase however remains elusive hitherto and can hardly be realized in APT-symmetric thermal systems due to the existence of phase oscillation. Here we construct the counterpart of APT-symmetric diffusive systems, i.e., PT-symmetric diffusive systems, which can achieve complete suppression of thermal phase oscillation. We find the real coupling of diffusive fields can be readily established through a strong convective background, where the decay-rate detuning is enabled by thermal metamaterial design. Moreover, we observe phase transition of PT symmetry breaking in diffusive systems with the symmetry-determined amplitude distribution and phase regulation of coupled temperature fields. Our work uncovers the existence of PT-symmetry in dissipative energy exchanges and provides a unique approach for harnessing the mass transfer of particles, the wave propagation in strongly scattering systems as well as thermal conduction.