Combining the Trotter decomposition and a series expansion of the partition function with respect to Hund's exchange coupling, we develop a new quantum Monte Carlo (QMC) algorithm for multiorbital systems with spin and orbital rotational symmetries. While the conventional QMC method has difficulties to treat the spin-flip and the pair-hopping terms of the Hamiltonian, we show that our new approach enables us to simulate these terms efficiently.
To demonstrate this, we apply our algorithm for studying ferromagnetism in the two-orbital Hubbard model within dynamical mean field theory (DMFT).
Our results reveal how important it is to account for the correct SU(2) symmetry of Hund's exchange. Otherwise, i.e., for an Ising (Z2) symmetry, Curie temperatures are grossly overestimated.
We also calculate the t2g spectral functions of Sr2RuO4 by three-band DMFT calculations with tight-binding parameters from the local density approximation as input and with proper rotational symmetries, which has been impossible before.
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