Strong versus weak coupling duality and coupling dependence of the Kondo temperature in the two-channel Kondo model

We perform numerical renormalization group (NRG) as well as analytical calculations for the two-channel Kondo (2CK) model to obtain the dependence of the Kondo temperature T-K on the dimensionless (bare) spin exchange coupling g over the complete parameter range from g < 1 to g > 1. We show that there exists a duality between the regimes of small and large coupling. It is unique for the two-channel model and enables a mapping between the strong and the weak coupling cases via the identification g <-> 3/(2g), implying an exponential dependence of T-K on 1/g and g, respectively, in the two regimes. This agrees quantitatively with our NRG calculations where we extract T-K(g) over the complete parameter range and obtain a nonmonotonic T-K(g) dependence, strongly peaked at the 2CK fixed point coupling g(*). These results may be relevant for resolving the long-standing puzzle within the 2CK interpretation of certain random defect systems as to why no broad distribution of T-K is observed in those systems.