2001/07/02 by M. Feldbacher, Christoph Jurecka, C. Jurecka +4
Physics and Astronomy · #Advanced Condensed Matter Physics #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.66.045103
8 pages, 7 figures. Submitted to PRB
arxiv created 2001/07/02 · openalex publication_date 2002/07/09 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We consider the Kondo lattice model in two dimensions at half filling. In addition to the Fermionic hopping integral t and the superexchange coupling J the role of a Coulomb repulsion U in the conduction band is investigated. We find the model to display a magnetic order-disorder transition in the U\ensuremath-J plane with a critical value of Jc which is decreasing as a function of U. The single-particle spectral function A(\stackrel\ensuremath→k,\ensuremathω) is computed across this transition. For all values of J>0, and apart from shadow features present in the ordered state, A(\stackrel\ensuremath→k,\ensuremathω) remains insensitive to the magnetic phase transition with the first low-energy hole states residing at momenta \stackrel\ensuremath→k=(\ifmmode±\else\textpm\fi\ensuremathπ,\ifmmode±\else\textpm\fi\ensuremathπ). As \stackrel\ensuremath→J0 the model maps onto the Hubbard Hamiltonian. Only in this limit does the low-energy spectral weight at \stackrel\ensuremath→k=(\ifmmode±\else\textpm\fi\ensuremathπ,\ifmmode±\else\textpm\fi\ensuremathπ) vanish such that the lowest energy hole states reside at wave vectors on the magnetic Brillouin-zone boundary. Thus we conclude that (i) the local screening of impurity spins determines the low-energy behavior of the spectral function and (ii) one cannot deform continuously the spectral function of the half-filled Hubbard model at J=0 to that of the Kondo insulator at J>Jc. Our results are based on both T=0 Quantum Monte-Carlo simulations and a bond-operator mean-field theory.