Fermi Surface Evolution Across Multiple Charge Density Wave Transitions   in ErTe3
  The Fermi surface (FS) of ErTe3 is investigated using angle-resolved photoemission spectroscopy (ARPES). Low temperature measurements reveal two incommensurate charge density wave (CDW) gaps created by perpendicular FS nesting vectors. A large Delta_1 = 175 meV gap arising from a CDW with c* - q_CDW1 ~ 0.70(0) c* is in good agreement with the expected value. A second, smaller Delta_2 = 50 meV gap is due to a second CDW with a* - q_CDW2 ~ 0.68(5) a*. The temperature dependence of the FS, the two gaps and possible interaction between the CDWs are examined. 
R.G. Moore, V. Brouet, R. He, D.H. Lu, N. Ru, J.-H. Chu, I.R. Fisher,   Z.-X. Shen