Low temperature heat transport was used to investigate the ground state of high-purity single crystals of the lightly-doped cuprate YBa2Cu3O6.33. Samples were measured on either side of the superconducting phase boundary, in both zero and applied magnetic field. We report the observation of delocalized fermionic excitations at zero energy in the non-superconducting state, which shows that the ground state of underdoped cuprates is metallic. Its low-energy spectrum appears to be similar to that of the d-wave superconductor, i.e. nodal. The insulating ground state observed in underdoped La2−xSrxCuO4 is attributed to the competing spin-density-wave order present in that system.
@article{arxiv.cond-mat/0501247,
title = {Delocalized fermions in underdoped cuprates},
author = {Mike Sutherland and S. Y. Li and D. G. Hawthorn and R. W. Hill and F. Ronning and M. A. Tanatar and J. Paglione and H. Zhang and Louis Taillefer and J. DeBenedictis and Ruixing Liang and D. A. Bonn and W. N. Hardy},
journal= {arXiv preprint arXiv:cond-mat/0501247},
year = {2009}
}
Comments
4 pages, 3 figures; published in Physical Review Letters