Fermi velocity engineering in graphene by substrate modification

TL;DR

This paper demonstrates a novel method to engineer the Fermi velocity in graphene by substrate modification, achieving the highest known Fermi velocity and providing a new approach for two-dimensional electron systems.

Contribution

It introduces a simple technique to modify Fermi velocity in graphene without changing charge carrier concentration, based on substrate dielectric properties.

Findings

Fermi velocity is inversely proportional to substrate dielectric constant.

Achieved the highest Fermi velocity for graphene on any substrate.

Fermi velocity behavior is distinct from ordinary Fermi liquids.

Abstract

The Fermi velocity is one of the key concepts in the study of a material, as it bears information on a variety of fundamental properties. Upon increasing demand on the device applications, graphene is viewed as a prototypical system for engineering Fermi velocity. Indeed, several efforts have succeeded in modifying Fermi velocity by varying charge carrier concentration. Here we present a powerful but simple new way to engineer Fermi velocity while holding the charge carrier concentration constant. We find that when the environment embedding graphene is modified, the Fermi velocity of graphene is (i) inversely proportional to its dielectric constant, reaching ~2.5$\times10^6$ m/s, the highest value for graphene on any substrate studied so far and (ii) clearly distinguished from an ordinary Fermi liquid. The method demonstrated here provides a new route toward Fermi velocity engineering in a variety of two-dimensional electron systems including topological insulators.