Fermiology of a 1D heavy electron metal
  We present a Quantum Monte Carlo (QMC) study of the 1D Kondo lattice at non-integer filling, i.e. a one-dimensional version of a heavy electron metal. For this special system the minus-sign problem turns out to be strongly reduced, which allows QMC simulations for temperatures as low as 1% of the conduction electron bandwidth. The single particle Green's function shows and intricate network of low-energy bands at low temperature, with a Fermi surface volume that comprises both c and f-electrons. As temperature increases the system evolves through two distinct crossover temperatures into a very simple band structure with one free c-electron band and a disconnected upper and lower Hubbard band for f-electrons. The f-electrons thus `drop out' of the Fermi surface volume as temperature increases. 
C. Groeber and R. Eder