Low Energy Electronic Structure of an Excitonic CDW Melted Novel Superconductor*

A superconducting (SC) state has very recently been observed upon successful doping of the charge-density wave (CDW) ordered triangular lattice TiSe$_2$ with copper. Using angle-resolved photoemission spectroscopy (ARPES) we studied the doping evolution of the electronic structure of Cu$_x$TiSe$_2$. The momentum space locations of the doped electrons that form the Fermi sea of the parent superconductor is identified. With increasing electron doping, we observe a significant rise of chemical potential which is found to destabilize the long range CDW order. At the same time the emergence of a large density of states in the form of a narrow electron pocket near the L- points of the Brillouin zone favors the onset of superconductivity within the BCS-Eliashberg scenario. With doping, we find that the kinematic nesting volume increases whereas the coherence of the CDW order sharply drops. The k- space electron distributions highlight the unconventional interplay of CDW to SC cross-over achieved through non-magnetic copper doping.