The new iron-based superconductor. Hao Hu The University of Tennessee Department of Physics and Astronomy, Knoxville Course: Advanced Solid State Physics II (Spring 2009) Instructor: Elbio Dagotto (Dated: March 22, 2009). Outline. Introduction
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The University of Tennessee Department of Physics and Astronomy,
Course: Advanced Solid State Physics II (Spring 2009)
Instructor: Elbio Dagotto
(Dated: March 22, 2009)
Y. Kamihara, et al, J. Am. Chem. Soc. 130, 3296 (2008).
Xianhui Chen reported on the arXiv preprint server (www.arXiv.org) a Tc=43K
Four days later, Zhong-Xian Zhao reported on the server that praseodymium oxygen fluorine iron arsenide has a Tc=52K
55 kelvin for the samarium compound grown under pressure
Schematic crystal structure of LaOFeAs.
Electron carriers generated by F-doping into oxygen sites are injected into FeAs metallic layers as a result of the large energy offset between these two layers.
Note that the carrier doping layer is spatially separated from the conduction layer.
They got Tc=43k at 4GPa on this F-doped LaOFeAs
Fe is sitting on a tetrahedral coordination. And Fe is formally divalent.
Hiroki Takahashi, et al, Nature 06972 (2008)
Plainly similar. The old and the new superconductors both contain planes of ions magnetized in opposite directions. In the older ones, electrons hop from copper to copper (arrow). For Fe-based SC, early results shows the As-Fe-As layer is responsible for the superconductivity.
Adrian Cho, Science 320, 870(2008)
The structural and electronic properties of the parent compound BaFe2As2 are closely related to LaFeAsO.
By hole doping potassium in this barium compound they get a Tc=38K
Marianne Rotter, et al, PRL 101 107006 (2008)
The red circles indicate the onset temperature of the P4=nmm to Cmma phase transition.
The black squares and green triangles designate the Ne´ el temperatures of Fe, TN (Fe), and Cerium, TN (Ce), respectively, as determined from neutron measurements
J.Zhao, et.al, Nature Mater. 7, 953(2008)
Simplified doping dependent phase diagrams of iron-based superconductors for both Ln-1111 and Ba-122 materials. The phases shown are the antiferromagnetic/spin density wave (AF/SDW) phase close to zero doping and the superconducting phase around optimal doping.
the superconducting phase is close to or overlapping with the magnetic phase.
Fermi surface maps of Ba1-xKxFe2As2 measured using respective excitation energies of hν=80 and 50 eV at T=14K
A sharp disagreement with band structure calculation
this paper reported that the electronic structure of Ba1-xKxFe2As2 revealed a reconstruction characterized by a (π, π) wave vector. This electronic order coexist with superconductivity and persists up to room temperature.
V.B.Zabolotnyy, et.al, Nature 457, 569(2009)
Topography reveals stripes. (a) 300 Å constant current topography reveals a stripe ordered region of the strontiumsample, bounded by unit cell height step edges in the upper left and lower right leading to non-atomically resolved regions. (b) 30 Å field of view more clearly showing resolution of atoms
Boyer et al, STM of (Sr1-xKx)Fe2As2arXiv:0806.4400