We consider the two channel Kondo model in the Emery-Kivelson approach, and calculate the total susceptibility enhancement due to the impurity $\chi_{ imp}=\chi-\chi_{ bulk}$. We find that $\chi_{ imp}$ exactly vanishes at the solvable point, in a completely analogous way to the singular part of the specific heat $C_{ imp}$. A perturbative calculation around the solvable point yields the generic behaviour $\chi_{ imp} \sim \log { 1 \over T}$, $C_{ imp} \sim T\log T $ and the known universal value of the Wilson ratio $R_W={ 8 \over 3}$. From this calculation, the Kondo temperature can be identified and is found to behave as the inverse-square of the perturbation parameter. The small field, zero-temperature behaviour $\chi_{ imp}\sim log { 1 \over h}$ is also recovered.
Categories: cond-mat