An efficient continuous-time quantum Monte Carlo impurity solver in Kondo Regime

An efficient continuous-time quantum Monte Carlo impurity solver with high acceptation ratio at low temperature is developed to study the strongly correlated heavy-fermion materials. In this solver, the imaginary time evolution operator for the high energy multiplets, which decays very rapidly with time, is approximated by a $\delta$ function, and as a result the virtual charge fluctuations of $f^n \rightarrow f^{n \pm 1}$ are all included without applying Schrieffer-Wolff transformation explicitly . As benchmarks, our algorithm perfectly reproduces the results for both Coqblin-Schriffeer and Kondo lattice models obtained by ct-$J$ method developed by Junya Otsuki et al. Furthermore, it allows us to study low energy physics of heavy-fermion materials directly without fitting the exchange coupling $J$ in the Kondo model. As an example, we test our solver on CeCoIn5, the famous heavy fermion material within the framework of LDA+DMFT to obtain its quasi-particle spectrum.