Analysis of spectroscopic data in kondo systems

The dynamics of the impurity spin in the Kondo problem has been studied in detail in the context of specific spectroscopic tools. The bosonized form of the Kondo Hamiltonian has been used to derive complete line-shape expressions relevant for interpreting NMR, Mossbauer, and ESR experiments. The calculation is equivalent to the so-called dilute-bounce-gas approximation in the treatment of the recently introduced spin-boson Hamiltonian. Analytical results are derived for longitudinal and transverse relaxation rates, NMR Knight shift, and the ESR g shift. From these, several known perturbative results, including the Abrikosov law, are recovered as special cases. The more general results derived here have been used to analyze a wide variety of spectroscopic data and the fits are found to be very satisfactory