• Electron crystallization;
  • Charge ordering;
  • Yb4As3


A necessary condition for electron crystallization is the dominance of the electronic Coulomb repulsion as compared with the kinetic energy. We show that 4f systems are good candidates for electron or hole crystallization to occur since the small radius of the 4f shell leads to small hybridizations and hence kinetic energy of the f electrons. Crystallization may take place in lattices with several equivalent 4f sites per unit cell when the electron or hole number is less than the number of sites. We give evidence that charge ordering in Yb4As3 is an example of the mechanism considered here. We also compare it with those considered by Wigner, Verwey, Mott and Hubbard.