Computing momentum-dependent susceptibilities in the dynamical mean-field theory (DMFT) requires solving the Bethe-Salpeter equation, which demands large computational cost. Exploiting the strong-coupling feature of local fluctuations, we derive a simplified formula that can be solved at a considerably lower cost. The validity and the physical meaning of the formula are confirmed by deriving the effective intersite interactions in the strong-coupling limit, such as the kinetic exchange and RKKY interactions. Furthermore, numerical calculations for single-orbital and multiorbital models demonstrate surprisingly wider applicability including a weak-coupling region. Based on this formula, we propose three levels of practical approximations that can be chosen depending on complexity of problems. Simpler evaluations of spin and orbital susceptibilities in multiorbital systems thus become possible within DMFT.Computing momentum-dependent susceptibilities in the dynamical mean-field theory (DMFT) requires solving the Bethe-Salpeter equation, which demands large computational cost. Exploiting the strong-coupling feature of local fluctuations, we derive a simplified formula that can be solved at a considerably lower cost. The validity and the physical meaning of the formula are confirmed by deriving the effective intersite interactions in the strong-coupling limit, such as the kinetic exchange and RKKY interactions. Furthermore, numerical calculations for single-orbital and multiorbital models demonstrate surprisingly wider applicability including a weak-coupling region. Based on this formula, we propose three levels of practical approximations that can be chosen depending on complexity of problems. Simpler evaluations of spin and orbital susceptibilities in multiorbital systems thus become possible within DMFT.

arXiv:1812.10918Physical review. B./Physical review. BApr 23, 201926 citations

Variational principle for dynamic susceptibilities

G�nter Sauermann

Physica A Statistical Mechanics and its ApplicationsSep 1, 19794 citations

Dynamical susceptibilities in the strong coupling approach: A general scheme and the Falicov–Kimball model

Andrij M. Shvaika

A general scheme to calculate dynamical susceptibilities of strongly correlated electron systems within the dynamical mean eld theory is developed.The approach is based on an expansion over electron hopping around the atomic limit (within the diagrammatic technique for site operators: projection and Hubbard ones) in in nite dimensions.As an example, the Falicov{Kimball and simpli ed pseudospin-electron models are considered for which an analytical expressions for dynamical susceptibilities are obtained.A general scheme to calculate dynamical susceptibilities of strongly correlated electron systems within the dynamical mean eld theory is developed.The approach is based on an expansion over electron hopping around the atomic limit (within the diagrammatic technique for site operators: projection and Hubbard ones) in in nite dimensions.As an example, the Falicov{Kimball and simpli ed pseudospin-electron models are considered for which an analytical expressions for dynamical susceptibilities are obtained.

arXiv:cond-mat/0203492Journal of Physical StudiesJan 1, 200115 citations

Strong-Coupling Expansion and Effective Hamiltonians

Frédéric Mila, Kai Phillip Schmidt

arXiv:1005.2495Springer series in solid-state sciencesSep 29, 201022 citations

On the weak coupling limit problem

Luigi Accardi, A. Frigerio, Yun Gang Lu

Lecture notes in mathematicsJan 1, 198915 citations

Strong-coupling theory for the thermodynamics of spin-1 planar magnetic chains

N. Papanicolaou, P Spathis

Earlier work on the $T=0$ dynamics of spin-1 chains with a strong easy-plane anisotropy is extended to include thermodynamics. Thus we carry out a systematic strong-coupling expansion to obtain analytical approximations for the spectrum of elementary excitations, the specific heat, and the magnetic susceptibility. Comparison with numerical data for the specific heat available in some important special cases indicates that our result is accurate for practically the entire temperature range. Similarly our calculation of the magnetic susceptibility reproduces to leading order a result obtained earlier through a molecular-field approximation and provides a definite improvement by including the two-loop correction. These theoretical predictions are directly relevant for a number of magnetic materials of current experimental interest.Earlier work on the $T=0$ dynamics of spin-1 chains with a strong easy-plane anisotropy is extended to include thermodynamics. Thus we carry out a systematic strong-coupling expansion to obtain analytical approximations for the spectrum of elementary excitations, the specific heat, and the magnetic susceptibility. Comparison with numerical data for the specific heat available in some important special cases indicates that our result is accurate for practically the entire temperature range. Similarly our calculation of the magnetic susceptibility reproduces to leading order a result obtained earlier through a molecular-field approximation and provides a definite improvement by including the two-loop correction. These theoretical predictions are directly relevant for a number of magnetic materials of current experimental interest.

Physical review. B, Condensed matterDec 1, 199525 citations

Earlier work on the

T=0

dynamics of spin-1 chains with a strong easy-plane anisotropy is extended to include thermodynamics. Thus we carry out a systematic strong-coupling expansion to obtain analytical approximations for the spectrum of elementary excitations, the specific heat, and the magnetic susceptibility. Comparison with numerical data for the specific heat available in some important special cases indicates that our result is accurate for practically the entire temperature range. Similarly our calculation of the magnetic susceptibility reproduces to leading order a result obtained earlier through a molecular-field approximation and provides a definite improvement by including the two-loop correction. These theoretical predictions are directly relevant for a number of magnetic materials of current experimental interest.