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STM/STS, HiKE, ARPES and Optics on pnictide superconductors

In February 2008 a Japanese research group reported superconductivity in a structure containing FeAs layers. The transition temperature of this new family of superconductors quickly increased to 55K, well above the BCS limit for superconductivity. Currently the mechanism behind the superconductivity (for instance the pairing symmetry of the Cooper pairs) is under hot debate. With a combined effort of scanning tunneling microscopy and spectroscopy (STM/STS), high kinetic energy photoemission (HiKE), angle resolved photoemission (ARPES) and Optics measurements, a better understanding of the physics behind the pnictide superconductors is investigated. The crystals used in this research are home-grown by Yinkai Huang using a self-flux technique.

topography of Ba-122 pnictide superconductor, BaFeCoAs
1.) Topography of Ba-122 		Ba-122 core level spectrum
2.) Ba-122 core level spectrum 		gap spectra of ba-122
3.) Typical Ba-122 crystals

This project is the main focus of the Postdoc research of Erik van Heumen and the PhD research carried out by Freek Massee. For more information, please contact Erik van Heumen or Freek Massee

Publications

Optical properties of BaFe2-xCoxAs2
E. van Heumen, Y. Huang, S. de Jong, A. B. Kuzmenko, M. S. Golden and D. van der Marel
EPL 90, 37005 (2010) pdf (416 kB)

Orbital character variation of the Fermi surface and doping dependent changes of the dimensionality in BaFe2-xCoxAs2 from angle-resolved photoemission spectroscopy
S. Thirupathaiah, S. de Jong, R. Ovsyannikov, H. A. Dürr, A. Varykhalov, R. Follath, Y. Huang, R. Huisman, M. S. Golden, Yu-Zhong Zhang, H. O. Jeschke, R. Valentí, A. Erb, A. Gloskovskii, and J. Fink
Phys. Rev. B 81, 104512 (2010) pdf (2.95 MB)

Droplet-like Fermi surfaces in the anti-ferromagnetic phase of EuFe2As2, an Fe-pnictide superconductor parent compound
S. de Jong, E. van Heumen, S. Thirupathaiah, R. Huisman, F. Massee, J. B. Goedkoop, R. Ovsyannikov, J. Fink, H. A. Dürr, A. Gloskovskii, H. S. Jeevan, P. Gegenwart, A. Erb, L. Patthey, M. Shi, R. Follath, A. Varykhalov and M. S. Golden
EPL 89, 27007 (2010) pdf (1.2 MB)

Cleavage surfaces of the BaFe2-xCoxAs2 and FeySe1-xTex superconductors:
A combined STM plus LEED study
F. Massee, S. de Jong, Y. Huang, J. Kaas, E. van Heumen, J.B. Goedkoop and M.S. Golden
Phys. Rev. B 80, 140507(R) (2009) pdf (460 kB)

Nanoscale superconducting gap variations and lack of phase separation in optimally doped BaFe1.86Co0.14As2
F. Massee, Y. Huang, R. Huisman, S. de Jong, J.B. Goedkoop, M.S. Golden
Phys. Rev. B 79, 220517(R) pdf (2.14 MB)

A high resolution, hard X-ray photoemission investigation of BaFe2As2: moderate influence of the surface and evidence for a low degree of Fe 3d - As 4p hybridization of the near-EF electronic states
S. de Jong, Y. Huang, R. Huisman, F. Massee, S. Thirupathaiah, M. Gorgoi, R. Follath, J. B. Goedkoop, and M. S. Golden
Phys. Rev. B 79, 115125 pdf (356 kB)