Invitation Only
Talk 1:
Diagrammatic treatment of spatial correlations beyond an interacting reference system: the D-TRILEX approach
Evgeny Stepanov, Ecole Polytechnique
Local approximations to electronic correlations, such as those provided by dynamical mean-field theory (DMFT), are a standard approach for addressing correlated multi-orbital systems. However, attempts to go beyond this local picture are often associated with expensive numerical calculations. To resolve this problem, we have developed the dual triply-irreducible local expansion (D-TRILEX) method [PRB 100, 205115 (2019); PRB 103, 245123 (2021); SciPost Phys. 13, 036 (2022)], which allows for a consistent diagrammatic treatment of leading non-local charge, spin, and orbital fluctuations beyond DMFT. In this talk, I will briefly introduce the D-TRILEX formalism and after that discuss the most prominent applications of the method in- and out-of-equilibrium.
Talk 2:
Nonequilibrium DMFT impurity solver via the Auxiliary Master Equation Approach: functional interpolation and multi-orbital mixed-configuration
extensions
Enrico Arrigoni, TU Graz
The auxiliary master equation approach (AMEA) [1] provides an efficient and controlled route to solving steady-state nonequilibrium dynamical mean-field theory (DMFT) impurity problems by mapping the physical impurity to a finite open quantum system with bath orbitals and a Markovian environment. This mapping achieves exponentially accurate fits of the hybridisation function, enabling reliable access to Keldysh Green’s functions and transport observables in nonequilibrium steady states.
After an overview of the approach, I will discuss two recent extensions: (i) a functional interpolation [2] expansion that stabilises and refines the hybridisation fit across frequencies, reducing the required bath size and systematic errors in the self energy and (ii) an attempt to approximately address multi-orbital impurities within a mixed configuration approximation [3].