Nanoscale magnetic phenomena driven by electron correlations

• Applicant: Professor Dr. Alexander Lichtenstein
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 267605795

• Final Report Year: 2019

Final Report Abstract

We successfully analyzed the electronic structure of several adatoms adsorbed on metal surfaces and on graphene using first-principles computational methods. In particular, we found an explanation for the conflicting experimental results previously obtained for a holmium atom adsorbed on the surface of platinum. We formulated improvements to the employed computational methods, and implemented these improvements into our in-house computer codes and partly also to one publicly available code (SPR-KKR developed by prof. H. Ebert's group in Munich). We systematically compared two methods for numerical solution of the Anderson impurity model and showed that the exact diagonalization provides as accurate results as the quantum Monte Carlo method for the thermodynamic quantities at a fraction of the computational cost. We formulated and implemented a theory of the inelastic electron tunneling that is observed in scanning tunneling microscope. Using this theory we demonstrated that the simpler approximation used in the literature nowadays has to be generalized for adatoms with strong spin-orbit coupling. This generalization modifies the theoretical predictions of the lifetime of the magnetic states of the adatoms, which is a key quantity when evaluating suitability of a particular adatom-surface combination for a stable storage of magnetic information. The developed tools allowed us to also investigate the local electronic structure in bulk crystals as probed in core-level spectroscopy. We used this new capability to analyze how the 4f and 5f electrons participate in the chemical bonding in several lanthanide and actinide compounds.

Publications

• Electronic structure and core-level spectra of light actinide dioxides in the dynamical mean-field theory. Phys. Rev. B 92, 085125 (2015)
  J. Kolorenč, A. B. Shick, A. I. Lichtenstein
  
• Racah materials: role of atomic multiplets in intermediate valence systems. Scientific Reports 5, 15429 (2015)
  A. B. Shick, L. Havela, A. I. Lichtenstein, M. I. Katsnelson
  
• Tuning emergent magnetism in a Hund's impurity. Nature Nanotechnology 10, 958 (2015)
  A. Khajetoorians, M. Valentyuk, M. Steinbrecher, T. Schlenk, A. Shick, J. Kolorenč, A. Lichtenstein, T. O. Wehling, R. Wiesendanger, J. Wiebe
  
• Electronic structure and magnetism of samarium and neodymium adatoms on free-standing grapheme. Phys. Rev. B 94, 125113 (2016)
  A. L. Kozub, A. B. Shick, F. Maca, J. Kolorenc, A. I. Lichtenstein
  
• Metal-Oxygen Hybridization and Core-Level Spectra in Actinide and Rare-Earth Oxides. MRS Advances 1, 3007 (2016)
  J. Kolorenč
  
• Racah materials: Role of atomic multiplets and intermediate valence in f-electron systems. MRS Advances 1, 2967 (2016)
  A. I. Lichtenstein, J. Kolorenč, A. B. Shick, M. I. Katsnelson
  
• Magnetic character of holmium atom adsorbed on platinum surface. Scientific Reports 7, 2751 (2017)
  A. B. Shick, D. S. Shapiro, J. Kolorenč, A. I. Lichtenstein
  
• Cobalt adatoms on graphene: Effects of anisotropies on the correlated electronic structure. Phys. Rev. B 97, 085133 (2018)
  R. Mozara, M. Valentyuk, I. Krivenko, E. Şaşıoğlu, J. Kolorenč, A. I. Lichtenstein
  
• Role of nonspherical double counting in DFT+DMFT: Total energy and structural optimization of pnictide superconductors. Phys. Rev. B 97, 201116(R) (2018)
  O. Kristanovski, A. B. Shick, F. Lechermann, A. I. Lichtenstein