Department of Physics, University of California, Berkeley
Materials Sciences Division, Lawrence Berkeley National Lab
In 2008 a new class of high-temperature superconductor was discovered, based on iron. With a maximum critical temperature thus far of about 55 K, these new iron-based superconductors (with sub-classes including the “pnictide superconductors” and “chalcogenide superconductors”) have the highest superconducting temperatures outside of the cuprate family.
Iron-based superconductors are also notable for sharing many other characteristics with the cuprates, which do not appear in the majority of conventional superconductors. Both the cuprates and iron-based superconductors are layered materials. A neutron spin resonance has been observed in both types of materials. Both have similar phase diagrams: superconductivity only emerges after doping an antiferromagnetic parent state with electrons or holes.
Not all of the cuprate characteristics have a direct analogue in the iron-based superconductors, however. Iron-based superconductors are more three-dimensional than the cuprates in terms of their band structure and in terms of the electronic coupling between layers. The parent state of the iron-based superconductors is a conductor, whereas in cuprates the parent state is an antiferromagnetic insulator. Hole-doped cuprates exhibit a strange “pseudogap” state above the superconducting critical temperature, a state which is absent in iron-based superconductors.
Our research group is interested in using photoemission, spin-ARPES, and time-resolved ARPES to tease out the subtleties of these similarities and differences. We hope to use this information to uncover the broader mechanism of high-temperature superconductivity in any material.
Core level and valence band study using angle-integrated photoemission on LaFeAsO0.9F0.1
D.R. Garcia, C. Jozwiak, C.G. Hwang,A. Fedorov, S.M. Hanrahan, S.D. Wilson, C.R. Rotundu, B.K. Freelon, R.J. Birgeneau, E. Bourret-Courchesne and A. Lanzara
Phys. Rev. B 78, 245119 (2008)