The evolution of Ca2−xNaxCuO2Cl2 from Mott insulator to superconductor was studied using angle-resolved photoemission spectroscopy. By measuring both the excitations near the Fermi energy as well as non-bonding states, we tracked the doping dependence of the electronic structure and the chemical potential with unprecedented precision. Our work reveals failures in the conventional quasiparticle theory, including the broad lineshapes of the insulator and the apparently paradoxical shift of the chemical potential within the Mott gap. To resolve this, we develop a model where the quasiparticle is vanishingly small at half filling and grows upon doping, allowing us to unify properties such as the dispersion and Fermi wavevector with the behavior of the chemical potential.
@article{arxiv.cond-mat/0407002,
title = {Missing Quasiparticles and the Chemical Potential Puzzle in the Doping Evolution of the Cuprate Superconductors},
author = {K. M. Shen and F. Ronning and D. H. Lu and W. S. Lee and N. J. C. Ingle and W. Meevasana and F. Baumberger and A. Damascelli and N. P. Armitage and L. L. Miller and Y. Kohsaka and M. Azuma and M. Takano and H. Takagi and Z. -X. Shen},
journal= {arXiv preprint arXiv:cond-mat/0407002},
year = {2009}
}