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Space charge and screening in bilayer graphene

Research paper by Eugene B. Kolomeisky, Joseph P. Straley, Daniel L. Abrams

Indexed on: 06 Jul '16Published on: 06 Jul '16Published in: Physics - Mesoscopic Systems and Quantum Hall Effect



Abstract

Undoped bilayer graphene is a two-dimensional semimetal with a low-energy excitation spectrum that is parabolic in the momentum. As a result, the screening of an arbitrary external charge $Ze$ is accompanied by a reconstruction of the ground state: valence band electrons (for $Z>0$) are promoted to form a space charge around the charge while the holes leave the physical picture. The outcome is flat neutral object resembling the regular atom except that for $Z \gg 1$ it is described by a strictly linear Thomas-Fermi theory. This theory also predicts that the bilayer's static dielectric constant is the same as that of a two-dimensional electron gas in the long-wavelength limit.