Quantum critical dynamics of a magnetic impurity in a semiconducting host

Abstract: We have investigated the finite temperature dynamics of the singlet to doublet continuous quantum phase transition in the gapped Anderson impurity model using hybridization expansion continuous time quantum Monte-Carlo. Using the self-energy and the longitudinal static susceptibility, we obtain a phase diagram in the temperature-gap plane. The separatrix between the low temperature local moment phase and the high temperature generalized Fermi liquid phase of this phase diagram is shown to be the lower bound of the critical scaling region of the zero gap quantum critical point of interacting type. We have computed the nuclear magnetic spin-lattice relaxation rate, the Knight shift and the Korringa ratio, which show strong deviations for any non-zero gap from the corresponding quantities in the gapless Kondo screened impurity case.