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

• Final Report Year: 2021

Final Report Abstract

This project was devoted to advance on the application of first-principles many-body theory to challenging correlated materials systems, bridging the gap between the understanding of longstanding problems and the design of novel compounds. The elaborate combination of density functional theory (DFT) and dynamical mean-field theory (DMFT) proved successful in tackling both demanding research areas, and the given studies demonstrated routes for obvious connections. For the traditional compounds V2 O3 , MnSi, Sr2 RuO4 and NiO, we delivered new insights concerning their puzzling electronic structure. The role of electron-lattice coupling, different impurity doping, uniaxial strain, as well as the interplay of spin and orbital fluctuations was elucidated, providing deeper understanding of the complex multiorbital physics in these key materials of strong correlation physics. We furthermore identified the subgroup of mostly metallic delafossites as unique systems where the concept of a natural heterostructure in a bulk setting gives rise to highly sophisticated correlation physics. Coexistence of different electronic regimes, such as e.g. metallic and Mott-insulating layers, poses not only intriguing questions in the given bulk phase, but also opens up various routes for Mott materials design. We performed concrete steps in that direction and described different ways of engineering novel appearances of correlated matter. The interplay of charge-transfer and Mott-Hubbard physics in late transition-metal oxides was a further key aspect of this project. We first elaborated on it on a methodological level by introducing the DFT+sicDMFT method as an extension to standard DFT+DMFT for e.g. nickelates and cuprates. In this extended framework, the Coulomb interactions on the ligand sites are treated within the self-interaction correction (SIC) on a pseudopotential level. The surprising discovery of nickelate superconductivity in the last third of the project time offered a unique opportunity to apply the new scheme to a provoking materials problem. Our theoretical studies are at the fronline of this new exciting field of condensed matter physics and are believed valuable for its future development. This was a successful project with more than 15 peer-review publications, therefrom various in highlight journals such as Physical Review Letters, Physical Review X and Nature Communications. Furthermore, additional coverage of its scientific content has been provided through the award as NIC excellence project 2018 of the Julich Supercomputing Centre via the associated computing project, as well as through the designation of the Psi-k Highlight of the Month in November 2020.

Publications

• Orbital ordering of the mobile and localized electrons at oxygen-deficient LaAlO3 /SrTiO3 interfaces. ACS Nano 12, 7927 (2018)
  A. Chikina, F. Lechermann, M.-A. Husanu, M. Caputo, C. Cancellieri, X. Wang, T. Schmitt, M. Radovic and V. N. Strocov
  
• Uncovering the mechanism of the impurity-selective Mott transition in paramagnetic V2O3. Phys. Rev. Lett. 121, 106401 (2018)
  F. Lechermann, N. Bernstein, I. I. Mazin and R. Valentí
  
• A key role of correlation effects in the Lifshitz transition in Sr2 RuO4. Phys. Rev. B 100, 245139 (2019)
  M. E. Barber, F. Lechermann, S. V. Streltsov, S. L. Skornyakov, S. Ghosh, B. J. Ramshaw, N. Kikugawa, D. A. Sokolov, A. P. Mackenzie, C. W. Hicks and I. I. Mazin
  
• Interplay of charge-transfer and Mott-Hubbard physics approached by an efficient combination of self-interaction correction and dynamical mean-field theory. Phys. Rev. B 100, 115125 (2019)
  F. Lechermann, W. Körner, D. F. Urban and C. Elsässer
  
• Multiorbital Processes Rule the Nd1−x Srx NiO2 Normal State. Phys. Rev. X 10, 041002 (2020)
  F. Lechermann
  
• Unconventional Hund metal in a weak itinerant ferromagnet. Nat. Commun. 11, 3076 (2020)
  X. Chen, I. Krivenko, M. B. Stone, A. I. Kolesnikov, T. Wolf, D. Reznik, K. S. Bedell, F. Lechermann and S. D. Wilson