ARPES study on electronic evolution in Ca2-xNaxCuO2Cl2

Electronic evolution from an antiferromagnetic insulator to a high-Tc superconductor is revealed by angle-resolved photoemission spectroscopy experiments on tetragonal Ca2-xNaxCuO2Cl2 single crystals, which were grown for the first time under high pressures (≤5.5 GPa). In an underdoped superconductor (x=0.1), we found clear fingerprints of the parent magnetic insulator: a shadow band and a large gap-like structure. The results are most likely described by a 'chemical potential shift', which contrasts clearly with the 'pinned chemical potential' reported for the prototype La2-xSrxCuO4, demonstrating that the route to a high-Tc superconductor is not unique