Tieftemperatureigenschaften korrelierter Elektronensysteme mit orbitalen Freiheitsgraden

• Antragsteller: Professor Dr. Thomas Pruschke (†)
• Subject Area: Theoretische Physik der kondensierten Materie
• Term: from 2007 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 36841722

• Final Report Year: 2013

Final Report Abstract

Correlated electron systems show a rich variety in physical phenomena already on the level of the simplest implementations. Including in addition to the usual spin degrees of freedom of the electrons, which are responsible for magnetism and fascinating phenomena like Mott-Hubbard metal insulator transistions, the inclusion of orbital degrees of freedom adds another control tool to these systems. Competition or cooperation of spins and orbitals can vary the different phases rather dramatically, and also lead to new exciting phenomena when stimulated by external magnetic or electric fields. The colossal magneto resistance in the maganites is one particular example, as are the anomalous transport properties of Heavy Fermions, which, for example, exhibit extremely large thermo-electrical effects in the crossover regime between local moments in a host and the low-temperature Fermi liquid. Our research on the one hand provided novel insight in the mechanisms behind these effects, but on the other hand also uncovered new and partially unexpected phenomena. One example is charge ordering in a model related to the manganites. Up to now the major phenomena there were believed to be related to Jahn-Teller effect, but within our results other, correlation based, effects may also be responsible. Furthermore, recent experimental evidence for a strong tendency towards charge separation also seems to be compatible with our findings. Such phenomena usually allow to change system properties dramatically by just small variations of external control parameters like pressure or field, and are thus of great potential interest for devising new devices.

Publications

• Magnetic phases in the correlated Kondolattice model. Phys. Rev. B 76, 245101 (2007)
  R. Peters, T. Pruschke
  
• Magnetic Properties of the Extended Periodic Anderson Model. J. Phys. Soc. Jpn. 77, 033704 (2008)
  A Koga, N. Kawakami, R. Peters, T. Pruschke
  
• Quantum phase transitions in the extended periodic Anderson model. Phys. Rev. B 77, 045120 (2008)
  A. Koga, N. Kawakami, R. Peters, T. Pruschke
  
• Magnetic phase diagram of the Hubbard model with next-nearest-neighbour hopping. New J. Phys. 11 , 083022 (2009)
  R. Peters, T. Pruschke
  
• Splitting of the Kondo resonance in anisotropic magnetic impurities on surfaces. New J. Phys. 11, 053003 (2009)
  R. Zitko, R. Peters, T. Pruschke
  
• Orbital and magnetic order in the twoorbital Hubbard model. Phys. Rev. B 81, 035112 (2010)
  R. Peters, T. Pruschke