Fernando de Juan, Herbert A. Fertig
Phonon dispersions generically display non-analytic points, known as Kohn
anomalies, due to electron-phonon interactions. We analyze this phenomenon for
a zone boundary phonon in undoped graphene. When electron-electron interactions
with coupling constant $\beta$ are taken into account, one observes behavior
demonstrating that the electrons are in a critical phase: the phonon dispersion
and lifetime develop power law behavior with $\beta$ dependent exponents. The
observation of this signature would allow experimental access to the critical
properties of the electron state, and would provide a measure of its proximity
to an excitonic insulating phase.
View original:
http://arxiv.org/abs/1109.6375
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