The calculation of the impurity entropy for the exactly solvable two-channel Kondo model

Abstract

In this paper the entropy of the two-channel Kondo impurity is calculated. We demonstrate that the exactly solvable system of finite size can be described in terms of free fermions. None of these fermions is Majorana fermion. This allows us to find the impurity entropy $S(T, L)$ for arbitrary values of $T$ and $L$. As found before, $S(T=0, L=\infty)$ equals to $(1/2)\ln 2$. For finite $L$ the entropy shows a cross-over to the infinite-size behavior at $T>T_L=v_F/L$, in agreement with results of other researchers.