Tuning the effective fine structure constant in graphene: opposing effects of dielectric screening on short- and long-range potential scattering

TL;DR

This study demonstrates how adding a water overlayer in graphene modulates dielectric screening, leading to opposing effects on short- and long-range impurity scattering, and aligns well with theoretical models.

Contribution

It provides experimental evidence of dielectric screening effects on impurity scattering in graphene, highlighting the contrasting impacts on different scattering mechanisms.

Findings

Long-range impurity scattering mobility increased by over 30%.

Short-range impurity conductivity decreased by nearly 40%.

Minimum conductivity remained nearly unchanged.

Abstract

We reduce the dimensionless interaction strength in graphene by adding a water overlayer in ultra-high vacuum, thereby increasing dielectric screening. The mobility limited by long-range impurity scattering is increased over 30 percent, due to the background dielectric constant enhancement leading to reduced interaction of electrons with charged impurities. However, the carrier-density-independent conductivity due to short range impurities is decreased by almost 40 percent, due to reduced screening of the impurity potential by conduction electrons. The minimum conductivity is nearly unchanged, due to canceling contributions from the electron/hole puddle density and long-range impurity mobility. Experimental data are compared with theoretical predictions with excellent agreement.