Evolution of low-lying states in a doped CDW superconductor Cu_xTiSe₂

A superconducting state has recently been observed by only a slight copper doping (∼4%) of the metallic 2D commensurate charge-density-wave (CDW) phase of titanium diselenide. We have employed high-resolution photoemission spectroscopy (ARPES) to probe the evolution of low-lying states, providing evidence that the CDW in the doped system is not due to Fermi surface nesting. With increasing copper concentration, we observe a significant rise of the chemical potential and a manifold of low-lying states at the top of the Fermi sea with increasing particle-hole asymmetry. These effects taken together contribute to destabilize the observed commensurate electronic, possibly, excitonic order in the vicinity of the superconducting doping in this system.