Photoemission spectra of massless Dirac fermions on the verge of exciton   condensation
  Angle-resolved photoemission spectroscopy (ARPES) is a powerful probe of electron correlations in two-dimensional layered materials. In this Letter we demonstrate that ARPES can be used to probe the onset of exciton condensation in spatially-separated systems of electrons and holes created by gating techniques in either double-layer graphene or topological-insulator thin films. 
Stefan Rist, A.A. Varlamov, A.H. MacDonald, Rosario Fazio and Marco   Polini
cond-mat.str-el cond-mat.mes-hall