Magnetic impurity in topological nodal loop semimetals.

We investigate the Kondo effect of a spin-1/2 magnetic impurity in a topological nodal loop semimetal, in which band touchings form a nodal loop. The Fermi surface of a nodal loop semimetal is a torus or a drum-like structure, which is determined by chemical potential. When the chemical potential μ lies at the nodal loop ([Formula: see text]), the magnetic impurity and the conduction electrons form bound states only if their coupling exceeds a critical value. As the chemical potential is tuned away from the nodal loop, the Fermi surface becomes a torus or drum-like structure and the impurity and the host material always favor a bound state due to the finite density of state. Due to the anisotropic dispersion relationship in the energy band, the spatial spin-spin correlations [Formula: see text]([Formula: see text]) are of power-law decay with the decay rates proportional to [Formula: see text] and [Formula: see text] in different directions, respectively. The product [Formula: see text] and [Formula: see text] oscillates in coordinate space and the period is enhanced gradually as the Fermi surface evolves from a torus surface into a drum-like structure.