Visualizing Electronic Chirality and Berry Phases in Graphene Systems

SRC Users Y. Liu, G. Bian, T. Miller, and T.-C. Chiang recently published a paper titled “Visualizing Electronic Chirality and Berry Phases in Graphene Systems Using Photoemission with Circularly Polarized Light.” This paper is also described in a viewpoint article (see link below). In addition, first author Yang Liu also received a best poster award at SRC’s 2011 Users Meeting.  The work was done using ARPES with both circularly and linearly polarized light on the new U9 VLS-PGM beam line at SRC. 

Yang Liu receives best poster award
from SRC Director Joe Bisognano

See the abstract below:

Electronic chirality near the Dirac point is a key property of graphene systems, which is revealed by the spectral intensity patterns as measured by angle-resolved photoemission spectroscopy under various polarization conditions. Specifically, the strongly modulated circular patterns for monolayer (bilayer) graphene rotate by ± 90 deg (± 45 deg) in changing from linearly to circularly polarized light; these angles are directly related to the phases of the wave functions and thus visually confirm the Berry’s phase of pi (2* pi) around the Dirac point. The details are verified by calculations.

The paper is available online at: http://prl.aps.org/abstract/PRL/v107/i16/e166803

The viewpoint article is available at: http://physics.aps.org/articles/v4/79