Doping a Superconductor Isn't Like Doping a Semiconductor
Minute chemical substitutions are used to induce superconductivity in many materials, but the precise role of these dopants in iron-pnictide superconductors is an ongoing debate. In semiconductors, doping allows charge carrier concentrations to be controlled enabling electronic devices to be created. However, dopants in iron-arsenide superconductors do not simply impact charge carrier concentrations. Recent studies show that Co or Ni substitution for iron in BaFe2As2 produces superconducting samples, but Cu substitution does not lead to superconductivity at any doping level. Neutron scattering measurements have revealed that the magnetic order in Cu-doped samples is different and, combining experimental and theoretical results, these differences can be attributed to the stronger electron scattering effect of Cu, than for Co and Ni. This new understanding of the doping effects of transition metals may lead to the discovery of new, even higher temperature superconductors.
- M.G. Kim, J. Lamsal, T.W. Heithmann, G. S. Tucker, D. K. Pratt, S. N. Khan, Y. B. Lee, A. Alam, A. Thaler, N. Ni, S. Ran, S. L. Bud'ko, K. J. Marty, M. D. Lumsden, P. C. Canfield, B. N. Harmon, D. D. Johnson, A. Kreyssig, R. J. McQueeney, and A. I. Goldman. Effects of Transition Metal Substitutions on the Incommensurability and Spin Fluctuations in BaFe2As2 by Elastic and Inelastic Neutron Scattering. Physical Review Letters, 2012, 109, 167003. DOI: 10.1103/PhysRevLett.109.167003.