Fermi velocity renormalization in graphene probed by terahertz time-domain spectroscopy

TL;DR

This paper introduces terahertz time-domain spectroscopy as a fast, accurate, and scalable method to measure Fermi velocity renormalization and electrical properties of large-scale graphene on various substrates, enabling advanced applications.

Contribution

It demonstrates the use of THz-TDS to quantitatively analyze Fermi velocity renormalization and electrical parameters in graphene, including on substrates with low permittivity.

Findings

THz-TDS accurately probes Fermi velocity renormalization in graphene.

Electrical parameters of large-scale graphene can be extracted non-destructively.

Significant renormalization effects observed on low-permittivity substrates.

Abstract

We demonstrate terahertz time-domain spectroscopy (THz-TDS) to be an accurate, rapid and scalable method to probe the interaction-induced Fermi velocity renormalization {\nu}F^* of charge carriers in graphene. This allows the quantitative extraction of all electrical parameters (DC conductivity {\sigma}DC, carrier density n, and carrier mobility {\mu}) of large-scale graphene films placed on arbitrary substrates via THz-TDS. Particularly relevant are substrates with low relative permittivity (< 5) such as polymeric films, where notable renormalization effects are observed even at relatively large carrier densities (> 10^12 cm-2, Fermi level > 0.1 eV). From an application point of view, the ability to rapidly and non-destructively quantify and map the electrical ({\sigma}DC, n, {\mu}) and electronic ({\nu}F^* ) properties of large-scale graphene on generic substrates is key to utilize this material in applications such as metrology, flexible electronics as well as to monitor graphene transfers using polymers as handling layers.