Angle-resolved photoemission spectroscopy of Na-doped Ca2CuO2Cl2 single crystals: Fingerprints of a magnetic insulator in a heavily underdoped superconductor

摘要

Electronic evolution from an antiferromagnet to a high-Tc superconductor isrevealed by angle-resolved photoemission experiments on tetragonalCa(1.9)Na(0.1)CuO(2)Cl(2) single crystals, which were successfully grown forthe first time under high pressures. In this underdoped superconductor, wefound clear fingerprints of the parent insulator: a shadow band and a largepseudo-gap. These observations are most likely described by a "chemicalpotential shift", which contrasts clearly with the prevailing wisdom of the"pinned chemical potential" learned from the prototype La(2-x)Sr(x)CuO(4),demonstrating that the route to a high-Tc superconductor is not unique.