On the interpretation of manifold ultrafast dynamics in supported graphene

TL;DR

This study investigates ultrafast carrier dynamics in supported graphene on quartz using pump-probe measurements, revealing complex transmission behaviors and emphasizing the importance of intra- and inter-band effects for understanding relaxation processes.

Contribution

It provides new insights into the ultrafast optical response of supported graphene and highlights the significance of considering both intra- and inter-band contributions in modeling carrier relaxation.

Findings

Observation of decreased and enhanced probe transmission regimes.

An order of magnitude decrease in relaxation time at intermediate fluence.

Emphasis on the importance of intra- and inter-band effects in interpreting data.

Abstract

Understanding the ultrafast carrier dynamics of graphene on a substrate is a fundamental step in the development of graphene based opto-electronic devices. Here, we present ultrafast pump-probe measurements of supported graphene on quartz for a range of pump fluences that enable us to observe both decreased and enhanced probe transmission regimes on a femtosecond timescale. Unexpectedly, at an intermediate pump fluence, an order of magnitude decrease in the relaxation time constant of the differential transmission is observed. By employing a number of different models to interpret our experimental data, we demonstrate the importance of considering both intra- and inter-band contributions to the dynamical optical conductivity in order to extract a more physical relaxation time constant of hot optical phonons.