Correlated half-semimetal state in heavy fermion systems

Abstract

An ideal half-semimetal is characterized by a single spin-polarized electronic relativistic band across the Fermi energy. Realizing such state in the correlated electron systems depends not only on the way the time reversal symmetry breaks, but also on the electron filling and electron correlations. Here we investigate a honeycomb Anderson lattice model in the strong $f$ electron Coulomb interaction limit and with an additional $f$ electron ferromagnetic coupling. A generic phase diagram is presented showing the successive first-order phase transitions from the decoupled local ferromagnetic phase to the heavy fermion ferromagnetic and paramagnetic phases. In particular, the magnetic heavy fermion phase emerges in the intermediate region but with two magnetic states, identified as the ground state or metastable state with small or large spin magnetization, respectively. When the total electron filling is fixed at 3/8, the band crossing of the spin-down polarized channel in the small spin magnetization state locates at the Fermi energy, without the existence of other Fermi surfaces. Such ideal half-semimetal feature is protected by the Kondo gap in the spin-up polarized channel.