Epitaxial thin films of heavy-Fermion superconductor CeCoIn$_5$

Experimental studies of heavy-Fermion superconductors have been mainly concentrated in measurements using bulk crystals so far. Thin film fabrication process is a key to open new approaches to study fundamental physics, such as phase-sensitive measurements of order parameter using Josephson junctions, and controlling dimensionality of heavy Fermions by superlattices. Despite several attempts using different techniques and various substrates [1-3], epitaxial growth of Ce-based heavy-Fermion superconductors has been a challenging issue. Here we report on the first successful growth of epitaxial thin films of heavy-Fermion superconductor CeCoIn$_5$. By the combination of a ultra-high vacuum deposition technique using molecular beam epitaxy and the choice of proper substrate material with very good lattice matching with CeCoIn$_5$, we are able to fabricate epitaxial films whose transport properties reproduce the characteristic features of the bulk CeCoIn$_5$, including a sharp superconducting transition at 2.3 K. [1] O.\,K. Soroka {\it et al.}, J.\,Phys.: Condens.\,Matter {\bf 19}, 056006 (2007). [2] M. Izaki {\it et al.}, Appl. Phys. Lett. {\bf 91}, 122507 (2007). [3] A.\,G. Zaitsev {\it et al.}, Physica C {\bf 469}, 52 (2009).