KIAS workshop "From correlated electrons to nanoscale materials"

at Korea Institute for Advanced Study (KIAS), Seoul, Korea

• Hiro Tsunetsugu
  ISSP, University of Tokyo
  
  

  Title

  Low-energy effective model of "heavy-fermion" vanadium spinel LiV2O4

  Abstract

  The vanadium spinel LiV2O4 shows a “heavy-fermion-like” behavior, although it has no f-orbital electrons.  We have derived its low-energy effective model by an approach of real-space renormalization group type. When the origin of this unusual behavior is concerned, it is important to consider two characteristic features of this system: one is orbital degeneracy of partially filled t2g orbital and the other is the frustrated lattice structure, i.e., vanadium ions constitute the pyrochlore lattice.  Starting with a three-orbital Hubbard model on the pyrochlore lattice, we diagonalized it and obtained low-energy eigenstates in a tetrahedron unit and found that the ground state has a finite degeneracy in both of orbital and spin sectors in a realistic region of parameters.  Examining electron hopping and interactions between neighboring tetrahedron units, we have derived a low-energy effective Hamiltonian of t-J model type including competing exchange interactions of spin and orbital.  We expect that this model describes the low-energy crossover into the heavy-fermion-like state.  I discuss characters of this model including competition of various channels of interactions.