26 research outputs found
Generation of localized magnetic moments in the charge-density-wave state
We propose a mechanism explaining the generation of localized magnetic
moments in charge-density-wave compounds. Our model Hamiltonian describes an
Anderson impurity placed in a host material exhibiting the charge-density wave.
There is a region of the model's parameter space, where even weak Coulomb
repulsion on the impurity site is able to localize the magnetic moment on the
impurity. The phase diagram of a single impurity at T=0 is mapped. To establish
the connection with experiment thermodynamic properties of a random impurity
ensemble is studied. Magnetic susceptibility of the ensemble diverges at low
temperature; heat capacity as a function of the magnetic field demonstrates
pronounced low field peak. Both features are consistent with experiments on
orthorhombic TaS3 and blue bronze.Comment: 8 pages, 7 figure
Origin of the gap in the surface states of the antiferromagnetic topological insulator
We study the influence of the antiferromagnetic order on the surface states
of topological insulators. We derive an effective Hamiltonian for these states,
taking into account the space structure of the antiferromagnetic ordering. We
obtain a typical (gapless) Dirac Hamiltonian for the surface states if the
surface of the sample is not perturbed. However, a shift in the chemical
potential of the surface layer opens a gap in the spectrum away from Fermi
energy. Such a gap arises only in systems with a finite antiferromagnetic
order. We observe that the gap is robust against the surface disorder. The
obtained results are consistent with the recent experiments and density
functional theory calculations.Comment: 6 pages, 3 figure