Article

# Critical properties of the half-filled Hubbard model in three dimensions.

Institute for Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria.

Physical Review Letters (Impact Factor: 7.73). 12/2011; 107(25):256402. DOI: 10.1103/PhysRevLett.107.256402 Source: PubMed

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**ABSTRACT:**We have calculated the local magnetic susceptibility of one of the prototypical Fe-based superconductors (LaFeAsO) by means of the local density approximation + dynamical mean field theory as a function of both (imaginary) time and real frequencies with and without vertex corrections. Vertex corrections are essential for obtaining the correct $\omega$-dependence, in particular a pronounced low-energy peak at $\omega \sim 0.2 $eV, which constitutes the hallmark of the dynamical screening of a large instantaneous magnetic moment on the Fe atoms. In experiments, however, except for the case of x-ray absorption spectroscopy (XAS), the magnetic moment or the susceptibility represent typically the average over long time scales. In this respect, the frequency range of typical neutron experiments would be too limited to directly estimate the magnitude of the short-time moment.Physical review. B, Condensed matter 12/2011; 86(6). · 3.77 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We study thermodynamics of the 3D Hubbard model at half filling on approach to the N\'eel transition by means of large-scale unbiased Diagrammatic Determinant Monte Carlo simulations. We obtain the transition temperature in the strongly correlated regime, as well as temperature dependence of energy, entropy, double occupancy, and the nearest-neighbor spin correlation function. Our results improve the accuracy of previous unbiased studies and present accurate benchmarks in the ongoing effort to realize the antiferromagnetic state of matter with ultracold atoms in optical lattices.Physical review. B, Condensed matter 12/2012; 87(20). · 3.77 Impact Factor -
##### Article: The effect of six-point one-particle reducible local interactions in the dual fermion approach

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**ABSTRACT:**We formulate the dual fermion approach to strongly correlated electronic systems in terms of the lattice and dual effective interactions, obtained by using the covariation splitting formula. This allows us to consider the effect of six-point one-particle reducible interactions, which are usually neglected by the dual fermion approach. We show that the consideration of one-particle reducible six-point (as well as higher order) vertices is crucially important for the diagrammatic consistency of this approach. In particular, the relation between the dual and lattice self-energy, derived in the dual fermion approach, implicitly accounts for the effect of the diagrams, containing 6-point and higher order local one-particle reducible vertices, and should be applied with caution, if these vertices are neglected. Apart from that, the treatment of the self-energy feedback is also modified by 6-point and higher order vertices; these vertices are also important to account for some non-local corrections to the lattice self-energy, which have the same order in the local 4-point vertices, as the diagrams usually considered in the approach. These observations enlighten an importance of 6-point and higher order vertices in the dual fermion approach, and call for development of new schemes of treatment of non-local fluctuations, which are based on one-particle irreducible quantities.Journal of Physics A Mathematical and Theoretical 09/2012; 46(4). · 1.77 Impact Factor

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