arXiv subjects

Canio Noce

Publications and source records attributed to Canio Noce.

43 records · Page 3Linked to original sources

arXiv2003

Coexistence of ferromagnetism and singlet superconductivity via kinetic exchange

We propose a novel mechanism for the coexistence of metallic ferromagnetism and singlet superconductivity assuming that the magnetic instability is due to kinetic exchange. Within this scenario, the unpaired electrons which contribute to the magnetization have a positive feedback on the gain of the kinetic energy in the coexisting phase by undressing the effective mass of the carriers involved into the pairing. The evolution of the magnetization and pairing amplitude, and the phase diagram are first analyzed for a generic kinetic exchange model and then are determined within a specific case with spin dependent bond-charge occupation.

cond-mat.supr-con↗

arXiv2002

Generalized hole-particle transformations and spin reflection positivity in multi-orbital systems

We propose a scheme combining spin reflection positivity and generalized hole-particle and orbital transformations to characterize the symmetry properties of the ground state for some correlated electron models on bipartite lattices. In particular, we rigorously determine at half-filling and for different regions of the parameter space the spin, orbital and $η$ pairing pseudospin of the ground state of generalized two-orbital Hubbard models which include the Hund's rule coupling.

cond-mat.str-el↗

arXiv2002

Origin of the Optical Gap in Half-Doped Manganites

We have analyzed the coexisting charge and orbital ordering in half-doped manganites using a model which includes Coulomb and Jahn-Teller orbital polarization interactions. Most surprisingly, the gap in the optical conductivity is reduced by both on-site and intersite Coulomb interactions, but increases and explains the experimental results when the Jahn-Teller terms with orbital polarization are considered. The origin of this behavior is explained within a molecular model which arises in the limit of extreme topological frustration, when single electrons are confined to molecular units consisting of three orbitals.

cond-mat.str-el↗

arXiv2000

Variational study of the extended Hubbard-Holstein model on clusters of variable site spacing

We study the complete extended Hubbard-Holstein Hamiltonian on a four-site chain with equally spaced sites, with spacing-dependent electronic interaction parameters evaluated in terms of Wannier functions built from Gaussian atomic orbitals. By successive application of generalized displacement and squeezing transformations, an effective polaronic Hamiltonian is obtained, containing a purely phonon-induced, long-range intersite charge interaction. The phase diagrams for N=1,2,3,4 electrons have been determined by variational minimization of the sum of the electronic and the phononic energy, paying special attention to the effects of the above mentioned phonon-induced long-range interaction. To characterize the physics of each ground state, we have evaluated how variations of the site spacing affect the behavior of several correlation functions of experimental interest, with the aim of representing lattice deformation effects, either spontaneous or induced by external pressure.

cond-mat.str-el↗

arXiv2000

Phenomenological model for magnetotransport in a multi-orbital system

By means of the Boltzmann equation, we have calculated some magnetotransport quantities for the layered multi-orbital compound Sr$_2$RuO$_4$. The Hall coefficient, the magnetoresistance and the in-plane resistivity have been determined taking into account the Fermi surface curvature and different time collisions for the electrons in the $t_{2g}$ bands. A consistent explanation of the experimental results has been obtained assuming different relaxation rates for the in-plane transport with and without an applied magnetic field, respectively.

cond-mat.str-el↗

arXiv2000

Effect of magnetic fluctuations on the normal state properties of Sr_2RuO_4

We investigate the normal state transport properties of Sr$_2$RuO$_4 $ and we show that a consistent explanation of the experimental results can be obtained assuming that the system is near a quantum phase transition. Within the framework of a self-consistent spin fluctuation theory, we calculate the temperature variation of some relevant physical quantities and we discuss a possible microscopic origin of the quantum phase transition.

cond-mat.supr-con↗

arXiv2000

Distance-depending electron-phonon interactions

For a dimer with a non-degenerate orbital built from atomic wave functions of Gaussian shape we evaluate all the electron-phonon couplings derived from the one-body and two-body electronic interactions, considering both the adiabatic and extreme non-adiabatic limit. Not only the values of the coupling parameters in the two limits, but also the expressions of the corresponding terms in the Hamiltonian differ. Depending on the distance between the dimer ions, some of the two-body couplings are comparable, or even larger than the one-body ones.

cond-mat.str-el↗