Purcell effect at metal-insulator transitions

TL;DR

This study explores how the spontaneous emission rate of a quantum emitter is significantly enhanced near the insulator-metal transition in a composite medium, revealing the critical role of electromagnetic absorption at the percolation threshold.

Contribution

It demonstrates the maximum Purcell enhancement at the insulator-metal transition and elucidates the decay pathways influencing emitter lifetime in heterogeneous media.

Findings

Purcell factor can be enhanced by two orders of magnitude near the transition

Maximum Purcell factor occurs precisely at the insulator-metal transition

Radiation emission is dominated by electromagnetic absorption near the percolation threshold

Abstract

We investigate the spontaneous emission rate of a two-level quantum emitter next to a composite medium made of randomly distributed metallic inclusions embedded in a dielectric host matrix. In the near-field, the Purcell factor can be enhanced by two-orders of magnitude relative to the case of an homogeneous metallic medium, and reaches its maximum precisely at the insulator-metal transition. By unveiling the role of the decay pathways on the emitter's lifetime, we demonstrate that, close to the percolation threshold, the radiation emission process is dictated by electromagnetic absorption in the heterogeneous medium. We show that our findings are robust against change in material properties, shape of inclusions, and apply for different effective medium theories as well as for a wide range of transition frequencies.