1109.4056 (Gang Li et al.)

An efficient treatment of the high-frequency tail of the self-energy
function and its relevance for multi-orbital models    [PDF]

Gang Li, Werner Hanke

In this paper, we present an efficient and stable method to determine the
one-particle Green's function in the hybridization-expansion continuous-time
(CT-HYB) Quantum Monte Carlo method, within the framework of the dynamical
mean-field theory (DMFT). The high-frequency tail of the impurity self-energy
is replaced by a noise-free function determined by a dual-expansion around the
atomic limit. This method does not depend on the explicit form of the
interaction term. More advantageous, it does not introduce any additional
numerical cost to the CT-HYB simulation. We discuss the symmetries of the
two-particle vertex, which can be used to optimize the simulation of the
4-point correlation functions in the CT-HYB. Here, we adopt it to accelerate
the dual-expansion calculation, which turns out to be especially suitable for
the study of material systems with complicated band structures. As an
application, a 2-orbital Anderson impurity model with a general on-site
interaction form is studied. The phase diagram is extracted as a function of
the Coulomb interactions for two different Hund's coupling strengths. In the
presence of the hybridization between different orbitals, for smaller
interaction strengths, this model shows a transition from metal to
band-insulator. Increasing the interaction strengths, this transition is
replaced by a crossover from Mott insulator to band-insulator behavior.

View original: http://arxiv.org/abs/1109.4056