Magnetic impurities in spin-1/2 chains

The problem of a magnetic impurity embedded in a spin-1/2 chain has attracted a lot of attention in the literature. In particular, it has been suggested that this problem can be mapped into the two-channel Kondo problem, with a resulting overscreened spin-impurity susceptibility. Here we propose a different analytical approach to analyze the low-energy field theory, which allows us to extend our understanding of the single-impurity case beyond the known results for the two-channel Kondo problem.