Electronic coherence and coherent dephasing in the optical control of electrons in graphene

TL;DR

This paper measures the electronic coherence time in graphene using photocurrent interference, revealing a lower boundary of 22 fs and highlighting the role of coherent dephasing in quantum control of solid-state systems.

Contribution

It provides the first direct measurement of electronic coherence time in graphene using photocurrent interference, advancing understanding of quantum control in solid-state materials.

Findings

Electronic coherence time in graphene is approximately 22 fs.

Photocurrent interference reveals the role of quantum path interference.

Coherent dephasing masks the true coherence time.

Abstract

Electronic coherence is of utmost importance for the access and control of quantum-mechanical solid-state properties. Using a purely electronic observable, the photocurrent, we measure an electronic coherence time of 22 +/- 4 fs in graphene. The photocurrent is ideally suited to measure electronic coherence as it is a direct result of quantum path interference, controlled by the delay between two ultrashort two-color laser pulses. The maximum delay for which interference between the population amplitude injected by the first pulse interferes with that generated by the second pulse determines the electronic coherence time. In particular, numerical simulations reveal that the experimental data yield a lower boundary on the electronic coherence time and that coherent dephasing masks a lower coherence time. We expect that our results will significantly advance the understanding of coherent quantum-control in solid-state systems ranging from excitation with weak fields to strongly driven systems.