Tuning the effective fine structure constant in graphene: opposing effects of dielectric screening on short- and long-range potential scattering.
We reduce the dimensionless interaction strength alpha in graphene by adding a water overlayer in ultrahigh vacuum, thereby increasing dielectric screening. The mobility limited by long-range impurity scattering is increased over 30%, due to the background dielectric constant enhancement leading to a reduced interaction of electrons with charged impurities. However, the carrier-density-independent conductivity due to short-range impurities is decreased by almost 40%, 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.
Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742-4111, USA.
C
C
Jang
S
S
Adam
J-H
JH
Chen
E D
ED
Williams
S
S
Das Sarma
M S
MS
Fuhrer