Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 73: Focussed session: Frontiers of electronic structure theory: Strong correlations from first principles V (jointly with TT)

O 73.7: Talk

Thursday, March 29, 2012, 17:45–18:00, HE 101

Dynamical Vertex Approximation for Nanoscopic Systems — •Giorgio Sangiovanni, Angelo Valli, Georg Rohringer, Alessandro Toschi, and Karsten Held — TU Wien

With the aim of calculating strongly correlated materials more and more reliably, different novel approaches have been proposed in recent years. Quantum Cluster Theories turned out to be very successful for 2- and 3- dimensional Hubbard and related models. Complementary approaches, like Dual Fermion and Dynamical Vertex Approximation, classifiable as diagrammatic extensions of single-site Dynamical Mean Field Theory, become superior when long-range spatial correlations need to be accurately described. An interesting application of Dynamical Vertex Approximation is the one for nanoscopic systems [Phys. Rev. Lett. 104, 246402 (2010)]. The increasing complexity of nanoscopic systems and the possibility of tuning their physical properties through nano-engineering constitute a new challenge for theories, in particular when strong electronic correlations are involved. I will discuss how Dynamical Vertex Approximation can be applied to such problems. I will show how to model a quantum point contact with 110 atoms and present our finding that the contact becomes insulating already before entering the tunneling regime due to a local Mott-Hubbard transition occurring on the atoms which form the point contact. I will also present results for the realistic case of a manganite nano-cluster where we combined our algorithm with a one- electron Hamiltonian calculated within Density Functional Theory [Phys. Rev. Lett. 107, 197202 (2011)].