IQIM Postdoctoral and Graduate Student Seminar
Abstract: Electronic correlations play a central role in determining the ground state and response properties of many functional materials – ranging from Mott-Hubbard insulators to high-Tc superconductors and 2D materials. While density-functional theory (DFT) has been the workhorse for first-principles calculations for more than three decades, these complex materials elude a DFT description, both for practical and conceptual reasons. Dynamical frameworks, where frequency-dependent self-energies appear, as in many-body perturbation theory (MBPT) or dynamical mean-field theory (DMFT), provide a formally grounded approach to tackle excitations and electronic correlations.
As in the case of electronic structure, correlations play a central role in transport. These effects become dominant in ultra-pure2D monolayers at low temperature. In these conditions, the electrons behave as a viscous fluid and hydrodynamic effects become important, as shown in experiments.
In the first part of my talk, I discuss an alternative framework based on dynamical potentials, where a local and dynamical Hubbard functional is developed to address both spectral and thermodynamic properties in the presence of correlations. Such an approach is made possible by a computational framework we introduced – the algorithmic-inversion method on sum-over-poles – that supports dynamical formulations and their implementation into computer codes. With the theory, we obtain fully self-consistent results for thermodynamics and spectral properties in the paradigmatic correlated solid SrVO3, showing close agreement to the experiments. In addition, we study four Mott-Hubbard/charge-transfer transition-metal monoxides, highlighting the accuracy of the present approach against state-of-the art calculations and experiments.
Moving to transport properties for 2D monolayers, I present a novel treatment to calculate the conductivity from ab initio including electronic correlations. Starting from the Boltzmann-transport equation (BTE), we calculate Coulomb mediated scattering rates and integrals, to finally solve the BTE including electron-electron interactions. I present preliminary results on the scattering times of monolayer Graphene. This treatment can be used to predict viscosity from first principles and can also be generalized to include phonon-mediated electron scattering.
Lunch will be provided following the talk.