Abstract:
Despite being one of the earliest class of materials found to exhibit a
charge-density wave at sufficiently low temperatures, many properties of
the 2H-transition metal dichalcogenides are still not understood. One of
the most interesting puzzles is found from photoemission experiments: no
gap opens on the Fermi surface even in the nested regions going against
conventional CDW wisdom. We have provided a qualitative model which
explains how such gapless excitations can exist in the CDW phase.