Nature of Single Particle States in Disordered Graphene

<strong>Seminar of the School of Physical Sciences</strong> <strong>Nature of Single Particle States in Disordered Graphene</strong> <strong>Arti Garg&nbsp;</strong> (Saha Institute of Nuclear Physics, Kolkata) Date:&nbsp;<strong>December 5, 2016</strong> <strong>Abstract:</strong>&nbsp;It is well known that the Dirac states in graphene evade Anderson localization in the presence of weak long range charge impurities. But the nature of single particle states away from the Dirac point has not been explored in detail so far. Does a higher energy state, away from the Dirac point, get localized in the presence of an infinitesimal strength of disorder, as expected for a conventional 2D system or does it evade localization like a Dirac state? In this talk, I will focus on these questions and demonstrate that not only the Dirac state but all the single particle states remain extended in the presence of weak long range impurities due to generic anti-localization effects and prohibited backscattering events. A threshold strength V_{th} of disorder is required to localize a state with energy E since the random potential needs to scatter an electron from point \vec{k} on an equal energy contour of energy E to point -\vec{k} on it. Therefore, though states near the band center remain extended for weak to intermediate values of disorder strength, states near the band edge show extended nature only for weak disorder basically resulting in a mobility edge in this 2d system.