Physics

Dr. Anand Kamlapure
Radboud University, Nijmegen

Abstract:
Magnetic impurity interacting with Cooper pairs in a superconductor has pair breaking effects which produce sub-gap states, so-called Yu-Shiba-Rusinov (YSR) states within superconducting energy gap. Recent studies of interacting magnetic adatoms and chains on a superconductor have gained enormous interest due to the potential realization of topological superconductivity. In this talk, I will discuss our latest investigation on the artificially crafted multi-impurity Kondo clusters. We use a tip of a scanning tunneling microscope to tailor such clusters, in which, Fe adatoms are exchange-coupled to the assembly of interstitial Fe atoms on oxygen reconstructed Ta (100) surface. These clusters show the signatures of Kondo screening and the YSR states in the tunneling spectroscopy measurements. With the help of numerical renormalization group (NRG) calculations, we show that the observed behavior can be qualitatively reproduced by a two-impurity Kondo system whose inter-impurity antiferromagnetic interaction J is adjusted by the number of interstitial Fe atoms in the assembly. When driving the system from the regime of two decoupled Kondo singlets (small J) to that of an antiferromagnetic dimer (large J), the YSR state shows a characteristic cross-over in its energetic position and particle-hole asymmetry.