FeAs-Superconductors
The story of iron pnictides (FeAs) started in Feb. 2008, when Kamihara reported Superconductivity in the LaOFeAs (La1111) system at 26 K. The parent compound LaOFeAs is not superconducting, but upon replacing some of the oxygen by fluorine, the material becomes superconducting. Subsequent research from other groups suggests that replacing Lanthanum in LaFeAsO with other rare earth elements such as Cerium, Samarium, Neodymium and Praseodymium leads to superconductivity up to 52 K. Naturally, these new iron pnictides have generated enormous interest, both from theoretical and experimental sides. Since then many different methods have been used in order to investigate the electronic phase diagram of these materials in order to better understand the physics behind.
Materials under study:
- LaO1-xFxFeAs (1111 system)
- LiFeAs (111 system)
- FeSe (11 system)
- Ca(Fe1-xCox)2As2, Ba(Fe1-xCox)2As2 (122 system with Co and also Na doped)
- KFe2As2
Our collaborations:
Selected publications:
- The electronic phase diagram of the LaO1-xFxFeAs superconductor, H. Luetkens, H.-H. Klauss, M. Kraken, F. J. Litterst, T. Dellmann, R. Klingeler, C. Hess, R. Khasanov, A. Amato, C. Baines, M. Kosmala, O. J. Schumann, M. Braden, J. Hamann-Borrero, N. Leps, A. Kondrat, G. Behr, J. Werner, B. Buechner Nature materials 8 (2009) pp. 305-309.
- Single Crystal Growth and Characterization of Superconducting LiFeAs, Igor Morozov, Alexander Boltalin, Olga Volkova, Alexander Vasiliev, Olga Kataeva, Ulrike Stockert, Mahmoud Abdel-Hafiez, Dirk Bombor, Anne Bachmann, Luminita Harnagea, Madeleine Fuchs, Hans-Joachim Grafe, Günter Behr, Rüdiger Klingeler, Sergey Borisenko, Christian Hess, Sabine Wurmehl, Bernd Büchner Cryst. Growth Des. 10 (2010) pp. 4428–4432.
- Local antiferromagnetic correlations in the iron pnictide superconductors LaFeAsO1-xFx and Ca(Fe1-xCox)2As2 as seen via normal-state, R. Klingeler, N. Leps, I. Hellmann, A. Popa, U. Stockert, C. Hess, V. Kataev, H.-J. Grafe, F. Hammerath, G. Lang, S. Wurmehl, G. Behr, L. Harnagea, S. Singh, B. Buechner, Physical Review B 81 (2010) pp. 24506/1-5.
- Critical current and vortex dynamics in single crystals of Ca(Fe1-xCox)2As2, A.K. Pramanik, L. Harnagea, S. Singh, S. Aswartham, G. Behr, S. Wurmehl, C. Hess, R. Klingeler, B. Buechner, Physical Review B 82 (2010) pp. 14503/1-7.
- Superconductivity without Nesting in LiFeAs, S. V. Borisenko, V. B. Zabolotnyy, D. V. Evtushinsky, T. K. Kim, I. V. Morozov, A. N. Yaresko, A. A. Kordyuk, G. Behr, A. Vasiliev, R. Follath, and B. Büchner, Phys. Rev. Lett. 105 (2010) 067002.
- Thermal expansion of RFeAsO (R=La,Ce,Pr,Sm,Gd), R. Klingeler, L. Wang, U. Koehler, G. Behr, C. Hess, B. Buechner, Journal of Physics: Conference Series 200 (2010) pp. 12088/1-4.
- Phase diagram of iron-arsenide superconductors Ca(Fe1-xCox)2As2 (0 <= x <= 0.2) L. Harnagea, S. Singh, G. Friemel, N. Leps, D. Bombor, M. Abdel-Hafiez, A. U. B Wolter, C. Hess, R. Klingeler, G. Behr, S. Wurmehl, B. Büchner, Physical Review B 83 (2011).
- Specific heat and upper critical fields in KFe2As2 single crystals, M. Abdel-Hafiez, S. Aswartham, S. Wurmehl, V. Grinenko, C. Hess, S.-L. Drechsler, S. Johnston, A.U.B. Wolter, B. Buechner, H. Rosner, L. Boeri, Physical Review B 85 (2012).
- Specific heat and angle-resolved photoemission spectroscopy study of the superconducting gaps in LiFeAs, U. Stockert, M. Abdel-Hafiez, D.V. Evtushinsky, V.B. Zabolotnyy, A.U.B. Wolter, S. Wurmehl, I. Morozov, R. Klingeler, S.V. Borisenko, B. Buechner, Physical Review B 83 (2011).
For further information please contact: Dr. Anja Wolter or Mahmoud Mohamed