Hidden Dimer in the Frenkel-Kontorova model
  The incommensurability of the supercritical Frenkel-Kontorova model is decomposed into a family of dimer type "defects" by appropriate decimations. Interestingly, this hidden dimer results in Bloch-wave type excitations of the renormalized chain which appear in the disguised form of multi-step phonon modes for the original system. We call these intriguing excitations stepon modes and conjecture that they play a key role in determining the localization boundary in systems exhibiting Anderson localization. 
Jukka A. Ketoja and Indubala I. Satija