Thin-film growth of the heavy-fermion superconductor CeCoIn5

Thin films of CeCoIn5 were deposited on different substrates by using molecular beam epitaxy and found superconductive with transition temperatures about 2 K. Their transport properties are comparable with those of the bulk material and the resistivity shows typical heavy fermion behaviour. The growth characteristics were studied by means of X-ray diffraction and scanning tunneling microscopy and revealed (001)-oriented growth with pronounced island formation. Based on the chemical composition of the films obtained using energy dispersive X-ray analysis a ternary phase formation diagram was deduced. The heavy fermion compound CeCoIn5 is a member of a recently discovered layered heavy fermion family with general formula CeMIn5 (M=Co,Ir,Rh). These compounds exhibit many ground states that have been observed in f-electron systems, including paramagnetism, antiferromagnetism, exotic ambient-pressure and pressure induced superconductivity. There exists a relationship to the high-Tc superconductors as well. The layered quasi-2D crystal structure of these materials and that of the high-Tc cuprates share common features with regard to their spin-dependent electronic excitation spectrum. The most direct technique to investigate the spectrum of these excitations is tunneling spectroscopy which benefits strongly from well-defined surface as presented by epitaxial thin films. (orig.)