Long-lived modulation of plasmonic absorption by ballistic thermal injection

TL;DR

This study reveals a novel energy transduction mechanism at metal/semiconductor interfaces under ultrafast excitation, where hot electrons transfer energy without charge transfer, supported by experimental and theoretical evidence.

Contribution

It provides the first direct measurement of electronic distributions in such systems and uncovers a new energy transfer process in non-equilibrium conditions.

Findings

Hot electrons transfer energy without charge transfer.

Ultrafast measurements reveal non-equilibrium energy dynamics.

Theoretical models support experimental observations.

Abstract

Energy and charge transfer across metal-semiconductor interfaces are the fundamental driving forces for a broad range of applications, such as computing, energy harvesting, and photodetection. However, the exact roles and physical separation of these two phenomena remains unclear, particularly in plasmonically-excited systems or cases of strong nonequilibrium. We report on a series of ultrafast plasmonic measurements that provide a direct measure of electronic distributions, both spatially and temporally, following optical excitation of a metal-semiconductor heterostructure. For the first time, we explicitly show that in cases of strong non-equilibrium, a novel energy transduction mechanism arises at the metal/semiconductor interface. We find that hot electrons in the metal contact transfer their energy to pre-existing electrons in the semiconductor, without transfer of charge. These experimental results findings are well-supported by both rigorous multilayer optical modeling and first-principle, ab initio calculations.