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

TL;DR

This study uses angle-resolved photoemission spectroscopy on Na-doped Ca2CuO2Cl2 to reveal how electronic structures evolve from an antiferromagnetic insulator to a superconductor, highlighting the role of chemical potential shifts.

Contribution

First successful growth of Na-doped Ca2CuO2Cl2 crystals enabling direct observation of electronic evolution in underdoped cuprates.

Findings

Identification of a shadow band and a large pseudo-gap in underdoped superconductor

Evidence supporting a chemical potential shift rather than pinning in electronic evolution

Demonstration that the route to high-Tc superconductivity varies among cuprates

Abstract

Electronic evolution from an antiferromagnet to a high-Tc superconductor is revealed by angle-resolved photoemission experiments on tetragonal Ca(1.9)Na(0.1)CuO(2)Cl(2) single crystals, which were successfully grown for the first time under high pressures. In this underdoped superconductor, we found clear fingerprints of the parent insulator: a shadow band and a large pseudo-gap. These observations are most likely described by a "chemical potential 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.