Research-Super Conductivity

Epitaxial Thin Films of New Superconductor, Ferropnictide

TEM micrographs and critical current density of an epitaxial pnictide thin film grown on LSAT substrate with SrTiO3 template.

The discovery of superconductivity with transition temperatures of 20K-50K in iron-based materials has initiated a flurry of activity to understand and apply these novel materials. A fundamental key to both basic understanding and applications is the growth and control of high-quality epitaxial thin films. We report novel template engineering using single-crystal intermediate layers of SrTiO3 and BaTiO3 grown on various perovskite substrates[1]. This has enabled genuinely epitaxial films of Co-doped BaFe2As2 with superior Jc of 4.5 MA/cm2 (4.2K) and strong c-axis flux pinning. Our advance in pnictide single-crystal film growth allows the design and control of pnictide superconducting films and heterostructures to probe the fundamental superconducting mechanisms of this unique class of materials. Our main tasks are to control pnictide thin film and oxide templates at the atomic level, to understand the relation between structure and superconducting properties, and to design and grow novel crystalline pnictide heterostructures tuned to take advantage of the superconducting structure/property relationships possible in this unique new superconductor.

"Template Engineering of Co-doped BaFe2As2 single-crystal thin films" S. Lee, J. Jiang, C. T. Nelson, C. W. Bark, J. D. Weiss, C. Tarantini, H. W. Jang, C. M. Folkman, S. H. Baek, A. Polyanskii, D. Abraimov, A. Yamamoto, Y. Zhang, X. Q. Pan, E. E. Hellstrom, D. C. Larbalestier, C. B. Eom, February 28 online issue of Nature Materials (2010) [link pdf]

"Weak link behavior of grain boundaries in Co-doped BaFe2As2 pnictide superconductors”, S. Lee, J. Jiang, J. Weiss, C.M Folkman, C.W. Bark, C. Tarantini, A Xu, D. Abraimov, A. Polyanskii, C. T. Nelson, Y. Zhang, S.H. Baek, H.W.Jang, A. Yamamoto, F, Kametani, X. Pan, E. Hellstrom, A. Gurevich, C. B. Eom, D. C. Larbalestier, Appl. Phys. Lett., 95, 212505 (2009) [link pdf]

Supported by US Department of Energy, The office of Basic Energy Sciences