Weak localization measurements of electronic scattering rates in Li-doped epitaxial graphene

TL;DR

This study uses weak localization measurements to separately quantify intra- and intervalley scattering rates in Li-doped epitaxial graphene, revealing how lithium adatoms influence electronic scattering and potentially modify the band structure.

Contribution

It provides the first detailed separation of intra- and intervalley scattering rates in Li-doped graphene using weak localization, and compares experimental results with tight-binding calculations.

Findings

Li deposition enhances intravalley scattering consistent with Coulomb effects

Intervalley scattering is also increased, partly due to extra carriers interacting with disorder

Discrepancies at high Li coverage suggest adatom-induced band structure modifications

Abstract

Early experiments on alkali-doped graphene demonstrated that the dopant adatoms modify the conductivity of graphene significantly, as extra carriers enhance conductivity while Coulomb scattering off the adatoms suppresses it. However, conductivity probes the overall scattering rate, so a dominant channel associated with long-range Coulomb scattering will mask weaker short-range channels. We present weak localization measurements of epitaxial graphene with lithium adatoms that separately quantify intra- and intervalley scattering rates, then compare the measurements to tight-binding calculations of expected rates for this system. The intravalley rate is strongly enhanced by Li deposition, consistent with Coulomb scattering off the Li adatoms. A simultaneous enhancement of intervalley scattering is partially explained by extra carriers in the graphene interacting with residual disorder. But differences between measured and calculated rates at high Li coverage may indicate adatom-induced modifications to the band structure that go beyond the applied model. Similar adatom-induced modifications of the graphene bands have recently been observed in ARPES, but a full theoretical understanding of these effects is still in development.