Strongly Correlated Materials Design

• Applicant: Dr. Frank Lechermann
• Subject Area: Theoretical Condensed Matter Physics ; Synthesis and Properties of Functional Materials ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Theoretical Chemistry: Molecules, Materials, Surfaces
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 325300529

Aspects of materials design become more and more relevant beyond the capabilities of conventional electronic structure theory on the effective single-particle level. This project therefore aims at the merger of materials science and many-body physics for realistic condensed matter systems. Fluctuating local moments, finite-lifetime effects or intricate spectral-weight transfers belong to phenomena to be incorporated and engineered in future materials developments. We will address this problem by efficient and powerful combinations of Kohn-Sham-based density functional theory with explicit many-body schemes such as dynamical mean-field theory and slave boson mean-field theory. By promoting the first-principles many-body approach to a large-scale framework, novel hybrid materials systems with potential technological relevance that benefit from manifest quantum many-body physics may be designed. We focus on the quantum-engineering possibilities arising in the context of oxide heterostructures and from the manipulation of correlated oxide surfaces. Band- and/or Mott-insulating compounds will be generated in different interface/surface geometries and doping scenarios. Materials of diverse transition-metal d-shell valence and varying crystal structure will be allied in order to investigate emerging physics in terms of novel phases and competing orders. Electronic reconstructions and subtle modification of correlations on oxide surfaces and in thin films will be explored. Focus will be on titanates, vanadates, and chromium oxides for the Mott-critical systems, while SrTiO3, TiO2 and ZnO will be key materials from the band-insulating regime. Extensions and combinations with 4f materials are additionally envisaged. Perturbations to ideal systems via point defects, strain or applied fields will enlarge the range of designing options and provide deeper insight in the key mechanism governing such challenging materials. The effect of spin-orbit coupling on the ordering processes will be studied and its interplay with electronic correlations unveiled. New mechanisms for Mott criticality or metamagnetism in e.g. ruthenates and iridates may emerge that go beyond the known bulk-based processes. Studying the various transport regimes is of vital importance for the materials design and we will shed light on temperature-dependent resistivity, thermopower as well as optical conductivity. Deviations from the conventional Fermi-liquid picture are most interesting and the goal is to find ways to optimize such regimes and to pave the road for future technological utilization. Finally we will examine the options for combining oxide-based materials with novel quasi-two-dimensional semiconductors or Graphene-like systems within heterostructure architectures. Prediction of band gaps, conductivities or correlation effects becomes a highly fascinating endeavour in this new materials playground.

• DFG Programme: Research Grants