Quantum Monte-Carlo and Series-Expansion Analysis of Spin-Models for Molecular Magnets

• Antragsteller: Professor Dr. Wolfram Brenig
• Fachliche Zuordnung: Theoretische Physik der kondensierten Materie
• Förderung: Förderung von 2006 bis 2009
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 25514662

• Erstellungsjahr: 2009

Zusammenfassung der Projektergebnisse

This project has lead to progress in our understanding of various properties of lowdimensional supramolecular magnets. Due to the tunability of their real-space structure as well as the wide variety of magnetic exchange interactions which can be realized in such magnets, they are an interesting bridge between pure single-molecule magnets and more conventional solid-state magnetic bulk materials. Using methods from large-scale computational theoretical physics, namely Quantum-Monte Carlo calculations based on the stochastic series expansion and high-order coupling constant expansions in terms of the magnetic exchange interactions we have investigated basic properties of these magnetic materials including thermodynamics, time-dependent phenomena, and quantum phases. In close collaboration with experimental researchers we have undertaken the first successful analysis of the quantum critical slowing-down at a magnetic field induced switching of a molecular spin-chain to full spin-polarization. We have investigated thermodynamic properties, magnetization switching and disorder phenomena in one- and two-dimensional coupled arrays of antiferromagnetic spin-dimers. Finally we have studied networks of tetrahedral spin-clusters. The latter studies have resolved a long-standing issue about the stability of the so-called sliding Luttinger liquid, which had been proposed as a two-dimensional unconventional quantum-state of matter. In contrast to previous claims, and using high-precision results from our series expansions we could show, that arbitrarily weak two-dimensional couplings were able to destabilize the sliding Luttinger liquid. Additionally we have found a novel spin-plaquette phase for certain ranges of inter-tetrahedral exchange couplings.

Projektbezogene Publikationen (Auswahl)

• Eur. Phys. J. B 53, 193 (2006)
  M. Arlego and W. Brenig
  
• Phys. Rev. B 73, 174415 (2006)
  C. Mennerich, H.-H. Klauss, M. Broekelmann, F. J. Litterst, C. Golze, R. Klingeler, V. Kataev, B. Büchner, S.-N. Grossjohann, W. Brenig, M. Goiran, H. Rakoto, J.-M. Broto, O. Kataeva, and D. J. Price
  
• Comp. Rend. Chim. 10, 79 (2007)
  W. Brenig
  
• Phys. Rev. B 75, 024409 (2007)
  M. Arlego and W. Brenig
  
• Phys. Rev. B 78, 224415 (2008)
  M. Arlego and W. Brenig
  
• Phys. Rev. B 79, 094409 (2009)
  S. Grossjohann and W. Brenig
  
• Phys. Rev. B 80, 045110 (2009)
  H. Kuehne, H.-H. Klauss, S. Grossjohann, W. Brenig, F.J. Litterst, A.P. Reyes, P.L. Kuhns, M.M. Turnbull, C.P. Landee