21 documents found, page 1 of 3
Superconductivity in the SU(N) Anderson lattice at U = infinity
Araújo, Miguel; Peres, Nuno; Sacramento, Pedro; Vieira, VítorWe present a mean-field study of superconductivity in a generalized N-channel cubic Anderson lattice at U=infinity taking into account the effect of a nearest-neighbor attraction J. The condition U=infinity; is implemented within the slave-boson formalism considering the slave bosons to be condensed. We consider the f-level occupancy ranging from the mixed valence regime to the Kondo limit and study the depende...
Specific heat of the periodic Anderson model: From weak to strong coupling
Peres, Nuno; Sacramento, Pedro; Araújo, MiguelWe study the temperature dependence of the specific heat in the periodic Anderson model as function of the on-site Coulomb interaction, hybridization, and position of the f electrons energy level. At strong coupling (U = infinity) we use slave bosons, whereas at weak coupling we use a simple Hartree-Fock decomposition. We find that both in the strong and weak coupling limits the specific heat of the system pres...
Changing the Topology of Electronic Systems Through Interactions or Disorder
Araújo, Miguel; Castro, Eduardo; Sacramento, PedroRecent work on the influence of interactions or disorder on the topological properties of insulators is reviewed. We show that a purely local interaction can cause topological transitions by renormalizing kinetic energy terms alone, without phase transitions associated with order parameters. Disorder is also a mean of changing the topology of Chern insulators, as it localizes every state except for those carryi...
Local-moment formation in the periodic Anderson model with superconducting corr...
Araujo, Miguel; Peres, Nuno; Sacramento, PedroWe study local-moment formation in the presence of superconducting correlations among the f electrons in the periodic Anderson model. Local moments form if the Coulomb interaction U > U-cr. We find that U-cr is considerable stronger in the presence of superconducting correlations than in the nonsuperconducting system. Our studs is done for various values of the f-level energy and electronic density. The smalles...
Effect of Majorana Fermions on Andreev Spectroscopy of Multiband Topological Su...
Silva, Ana; Araújo, Miguel; Sacramento, PedroWe introduce a model for a multiband topological superconductor with two orbitals per lattice site, in two spatial dimensions. Concentrating on the Andreev refection problem, the appropriate wave function matching conditions for an interface with a normal single-band metal were previously derived in the framework of a quantum waveguide theory. This theory retrieves the correct number of Majorana fermion states ...
Andreev spectroscopy of Majorana states in topological superconductors with mul...
Silva, Ana; Araújo, Miguel; Sacramento, PedroThe topological properties of a multiband topological superconductor in two dimensions are studied, when the latter is obtained by introducing electron pairing in an otherwise topological insulator. The type of pairing, doping and Fermi surface topology play an essential role. Considering the Andreev reflection problem, we use a previously developed quantum waveguide theory for multiorbital systems and find tha...
Hall conductivity as bulk signature of topological transitions in superconductors
Sacramento, Pedro; Araújo, Miguel; Castro, EduardoTopological superconductors (TSCs) may undergo transitions between phases with different topological numbers which are related to the presence of gapless (Majorana) edge states. In a TSC the charge Hall conductivity, σxy, is not quantized and evolves continuously between different topological phases. Here we show that in two-dimensional Z-TSC the derivatives of σ_xy display sharp features signaling the topologi...
Emergent Nesting of the Fermi Surface from Local-Moment Description of Iron-Pni...
Rodriguez, Jose; Araújo, Miguel; Sacramento, PedroWe uncover the low-energy spectrum of a t-J model for electrons on a square lattice of spin-1 iron atoms with 3dxz and 3dyz orbital character by applying Schwinger-boson-slave-fermion mean-field theory and by exact diagonalization of one hole roaming over a 4 × 4 × 2 lattice. Hopping matrix elements are set to produce hole bands centered at zero two-dimensional (2D) momentum in the free-electron limit. Holes ca...
Change of an insulator’s topological properties by a Hubbard interaction
Araújo, Miguel; Sacramento, Pedro; Castro, EduardoWe introduce two-dimensional fermionic band models with two orbitals per lattice site, or one spinful orbital, and which have a nonzero topological Chern number that can be changed by varying the ratio of hopping parameters. A topologically nontrivial insulator is then realized if there is one fermion per site. When interactions in the framework of the Hubbard model are introduced, the effective hopping paramet...
Anomalous Hall effect in superconductors with spin-orbit interaction
Sacramento, Pedro; Araújo, Miguel; Vieira, Vítor; Dugaev, Vitalii; Barnas, JosefWe calculate the anomalous Hall conductance of superconductors with spin-orbit (SO) interaction and with either uniform or local magnetization. In the first case, we consider a uniform ferromagnetic ordering in a spin-triplet superconductor, whereas, in the second case, we consider a conventional s-wave spin-singlet superconductor with a magnetic impurity (or a diluted set of magnetic impurities). In the latter...