Orbital, spin and charge fluctuations in layered oxide heterostructures

• Applicant: Professor Dr. Giorgio Sangiovanni
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 85460759

• Final Report Year: 2019

Final Report Abstract

The project joined the Research Unit in its second funding period and took soon the role of a sort of "DFT+DMFT factory" for the whole Research Unit. Density Functional Theory (DFT), Dynamical Mean Field Theory (DMFT) and their merger have been further developed, pushed to the limit of applicability to complex materials. The originally planned research on vanadium-oxides became soon a much broader and successful investigation on the diverse classes of materials present in the Research Unit. In compliance with the title of the project, we have been looking at the intertwined orbital, spin and charge physics of layered oxide heterostructures. The project has published papers on nickel heterostructures and as well as on the dimensionality crossover in the thickness-driven metal-insulator transition exhibited by iridium oxides. The intriguing many-body properties of the chromium (001 surface) and of iron films are the object of other publications of this project. We have also revisited the low-energy modeling of high-Tc superconductivity in cuprates. Further relevant results have been reported in a series of works on correlated oxides, culminated in the "Nature Communications paper" on iron and nickel at ambient and Earth's core pressure. Another series of publications regarded the understanding of Kondo molecules, in close collaboration. The work on nickel and iron has played a special role during the research project. In this extensive and deep analysis of the electronic and spin properties of nickel and iron we have moved to the forefront of the first-principle description of solids. We have indeed disclosed how electrons can exhibit strong correlation effects not because they are part of a partially-filled d-shell but because in nickel they are slowed down flat by the presence of regions in the bandstructure and hence experience a form of pre-localization. This has also specific consequences for the behavior under pressure and, according to our calculations, it contributes to the electron scattering inside the inner core of our planet. We propose it also as an important ingredient for the convection processes needed to sustain the geodynamo and to create the Earth's magnetic field. For the completion of this work also the cooperation with TU Wien in the framework of the DFG FOR has been a key point. The two papers in cooperation with another report on the Kondo properties of transition metal phthalocyanine molecules. As mentioned above, they constitute "experiment+theory" papers where the combined effort has allowed an understanding of the many-body processes at the basis of the scanning tunneling processes measured by the group of Matthias Bode. These two publications are well cited and led to a further paper of the same kind and on the same subject, published in the Nature Partner Journal "Quantum Materials" in 2018, i.e. after the end of the FOR. One further work on similar topics was published by the Postdoc researcher, Michael Karolak, hired in the framework of the FOR. The scientific output of our project belongs to the field of fundamental research. It does not only represent an achievement for this Research Unit, but it has contributed to the body of ideas that have flowed later into an SFB on topological and correlated electronics at surfaces and interfaces.

Publications

• Effective crystal field and Fermi surface topology: A comparison of d- and dp-orbital models, Phys. Rev. B 88, 195116 (2013)
  N. Parragh, G. Sangiovanni, P. Hansmann, S. Hummel, K. Held and A. Toschi
  
• Importance of d–p Coulomb interaction for high TC cuprates and other oxides, New Journal of Physics 16, 033009 (2014)
  P. Hansmann, N. Parragh, A. Toschi, G. Sangiovanni and K. Held
  
• Quantized electronic fine structure with large anisotropy in ferromagnetic Fe films, Phys. Rev. B 90, 035136 (2014)
  C. Seibel, A. Nuber, H. Bentmann, M. Mulazzi, P. Blaha, G. Sangiovanni and F. Reinert
  
• Relevance of Hybridization and Filling of 3d Orbitals for the Kondo Effect in Transition Metal Phthalocyanines, Nano Lett. 14, 3895 (2014)
  J. Kügel, M. Karolak, J. Senkpiel, P.-J. Hsu, G. Sangiovanni and M. Bode
  
• Nickel-titanium double perovskite: A three-dimensional spin-1 Heisenberg antiferromagnet, Phys. Rev. B 91, 075108 (2015)
  M. Karolak, M. Edelmann, and G. Sangiovanni
  
• Shifting the Voltage Drop in Electron Transport Through a Single Molecule, Phys. Rev. Lett. 115, 016802 (2015)
  S. Karan, D. Jacob, M. Karolak, C. Hamann, Y. Wang, A. Weismann, A. Lichtenstein and R. Berndt
  
• State identification and tunable Kondo effect of MnPc on Ag(001), Phys. Rev. B 91, 235130 (2015)
  J. Kügel, M. Karolak, A. Krönlein, J. Senkpiel, P.-J. Hsu, G. Sangiovanni and M. Bode
  
• Many-body effects on Cr(001) surfaces: An LDA+DMFT study, Phys. Rev. B 93, 195115 (2016)
  M. Schüler, S. Barthel, M. Karolak, A. I. Poteryaev, A. I. Lichtenstein, M. I. Katsnelson, G. Sangiovanni and T. Wehling
  
• Dimensionality-Driven Metal-Insulator Transition in Spin-Orbit-Coupled SrIrO3, Phys. Rev. Lett. 119, 256404 (2017)
  P. Schütz, D. Di Sante, L. Dudy, J. Gabel, M. Stübinger, M. Kamp, Y. Huang, M. Capone, M.- A. Husanu, V. N. Strocov, G. Sangiovanni, M. Sing and R. Claessen
  
• Local magnetic moments in iron and nickel at ambient and Earth’s core conditions, Nat. Commun. 8, 16062 (2017)
  A. Hausoel, M. Karolak, E. Şaşıoğlu, A. Lichtenstein, K. Held, A. Katanin, A. Toschi and G. Sangiovanni