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Updated: Apr 15, 2026

Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities

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Published on: July 24, 2015

Population inversion in monolayer and bilayer graphene.

Isabella Gierz¹, Matteo Mitrano, Jesse C Petersen

¹Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149 22761, Hamburg, Germany.

Journal of Physics. Condensed Matter : an Institute of Physics Journal

|April 4, 2015

Summary

Bilayer graphene exhibits long-lived population inversion, overcoming limitations in single-layer graphene for optoelectronic applications. This finding enhances possibilities for Terahertz light amplification using low-dimensional materials.

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Area of Science:

Condensed Matter Physics
Materials Science
Optoelectronics

Background:

Graphene's unique optical properties, including saturable absorption and negative optical conductivity in the Terahertz range, offer potential for optoelectronic devices.
Previous studies observed population inversion in single-layer graphene using time- and angle-resolved photoemission spectroscopy (tr-ARPES), but with a short relaxation time of ~130 femtoseconds, limiting applications like Terahertz light amplification.

Purpose of the Study:

To investigate population inversion dynamics in bilayer graphene.
To determine if bilayer graphene offers advantages over single-layer graphene for optoelectronic applications, particularly in Terahertz amplification.

Main Methods:

Utilized time- and angle-resolved photoemission spectroscopy (tr-ARPES) to directly observe and measure population inversion in bilayer graphene.
Developed a microscopic model to explain the observed phenomena.

Main Results:

Demonstrated significantly longer-lived population inversion in bilayer graphene compared to single-layer graphene.
Attributed the extended population inversion lifetime to the presence of a small band gap in bilayer graphene.

Conclusions:

Bilayer graphene exhibits promising characteristics for Terahertz optoelectronics due to its long-lived population inversion.
The findings suggest that optimizing pump photon energy and fluence could further enhance population inversion lifetimes in bilayer graphene, paving the way for advanced Terahertz devices.