Theorie für den Einfluß von elektronischen Korrelationen auf die elektronische und strukturelle Dynamik von Materialien

• Antragsteller: Professor Dr. Harald Jeschke
• Fachliche Zuordnung: Theoretische Physik der kondensierten Materie
• Förderung: Förderung von 2001 bis 2011
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 5348694

• Erstellungsjahr: 2011

Zusammenfassung der Projektergebnisse

The main focus of this Emmy Noether junior research group project was on the interplay of electronic correlations or electronic nonequilibrium and structural properties of materials. The unifying element of all investigations in this effort were electron-lattice effects. This original question has proven very fruitful. Some of the main results of the project can be summed up as follows: (i) The creation of coherent phonons in nanostructures with ultrashort laser pulses can lead to a large degree of control in microscopic structural manipulation. (ii) The prediction of TiOCl structures in the presence of high pressure and doping leads to a high degree of physical insight into the mechanisms of a metal insulator transition (under pressure) and an unusual insulator to insulator transition (with doping). The pressure induced metallization is linked to a dimerization and thus a lowering of the symmetry. Introduction of alkali atoms into the TiOCl structure leads to a structural distortion that localizes the added charges; this can be understood in terms of an ionic Hubbard model. (iii) An impurity solver based on equations of motion shows some promise as new method for the dynamical mean field theory impurity problem. (iv) The study of the two orbital Hubbard model with the dynamical cluster approximation yields interesting orbital selective phases. (v) The coexistence of frustrated with unfrustrated orbitals in multiband systems can lead to low ordered moment antiferromagnetic metallic phases. (vi) Structural investigations in the iron pnictide superconductors yield insight into microscopic mechanisms of pressure induced phase transitions and compare well to experiments. (vii) The structure prediction in coordination complexes sheds light on spin crossover transitions and could lead to the design of materials with target magnetic Hamiltonians. (viii) In organic charge transfer salts, an important revision in previously accepted triangular lattice Hubbard Hamiltonian parameters was achieved.

Projektbezogene Publikationen (Auswahl)

• Decoupling method for dynamical mean field theory calculations. Phys. Rev. B 71, 085103 (2005)
  H. O. Jeschke and G. Kotliar
  
• Microscopic model for transitions from Mott to spin-Peierls insulator in TiOCl. Phys. Rev. B 78, 205104 (2008)
  Y. Z. Zhang, H. O. Jeschke, and R. Valentí
  
• Two pressure-induced transitions in TiOCl: Mott insulator to anisotropic metal. Phys. Rev. Lett. 101, 136406 (2008)
  Y. Z. Zhang, H. O. Jeschke, and R. Valentí
  
• A fast impurity solver based on equations of motion and decoupling. Phys. Rev. B 79, 235112 (2009)
  Q. Feng, Y.-Z. Zhang, H. O. Jeschke
  
• Microscopic origin of pressure-induced phase transitions in iron-pnictide AFe2 As2 superconductors: an ab initio molecular dynamics study. Phys. Rev. B 80, 094530 (2009)
  Y. Z. Zhang, H. C. Kandpal, I. Opahle, H. O. Jeschke, and R. Valentí
  
• Revision of model parameters for κ-type charge transfer salts: An ab initio study. Phys. Rev. Lett. 103, 067004 (2009)
  H.C. Kandpal, I. Opahle, Y.-Z. Zhang, H. O. Jeschke, R. Valentí
  
• Similarities between structural distortions under pressure and chemical doping in superconducting BaFe2 As2. Nature Materials 8, 471 (2009)
  S. A. J. Kimber, A. Kreyssig, Y.-Z. Zhang, H. O. Jeschke, Roser Valent´ ı, F. Yokaichiya, E. Colombier, J. Yan, T. C. Hansen, T. Chatterji, R. J. McQueeney, P. C. Canfield, A. I. Goldman, and D. N. Argyriou
  
• Can the Mott insulator TiOCl be metallized by doping? A first-principles study. Phys. Rev. Lett. 104, 146402 (2010)
  Y.-Z. Zhang, K. Foyevtsova, H. O. Jeschke, M. U. Schmidt, R. Valentí
  
• Dynamical cluster approximation study of the anisotropic two-orbital Hubbard model. Phys. Rev. Lett. 104, 026402 (2010)
  H. Lee, Y.-Z. Zhang, H. O. Jeschke, R. Valentí, H. Monien
  
• Possible origin of the reduced ordered moment in iron pnictides: a Dynamical Mean Field Theory study. Phys. Rev. B 81, 220506(R) (2010)
  H. Lee, Y.-Z. Zhang, H. O. Jeschke, R. Valentí