Phase diagram of Yb doped CeCoIn₅

Inspired by the work of Nakatsuji et al., we explore the temperature-doping phase diagram of Ce_1-xYb_xCoIn₅. In the so-called 115 structure, Yb is a priory divalent and non-magnetic, and as a consequence doping CeCoIn5 with Yb removes a magnetic ion, as well as a charge at the same time. At low levels of Yb substitution, the lattice parameter remains almost unchanged. Our study will show if the Yb doped CeCoIn5 case can be analyzed similar to the case of La doping, where the system can be described by a separation of the Kondo response into a coherent lattice part, and an incoherent single ion contribution. CeCoIn5 is an example of a heavy fermion material that exhibits unconventional superconductivity, which is attributed to Kondo lattice coherence. The crystal also exhibits non-Fermi liquid behaviour due to an antiferromagnetic (AFM) instability near a quantum critical point (QCP). We treat this doping as the tuning parameter of the QCP. Wishing to probe only the magnetic specific heat, we removed all phonon contributions by using LaCoIn5 as the non-magnetic conjugate of the CeCoIn5. This consists of a series of high precision measurements of the specific heat on both compounds. This study aims at providing a better understanding of the superconducting state of Kondo materials in the 115 family exploiting a new tuning parameter.