Breakup of the Fermi surface near the Mott transition in low-dimensional systems

We investigate the Mott transition in weakly-coupled one-dimensional (1d) fermionic chains. Using a generalization of Dynamic Mean Field Theory, we show that the Mott gap is suppressed at some critical hopping $t_{\perp}^{c2}$. The transition from the 1d insulator to a 2d metal proceeds through an intermediate phase where the Fermi surface is broken into electron and hole pockets. The quasiparticle spectral weight is strongly anisotropic along the Fermi surface, both in the intermediate and metallic phases. We argue that such pockets would look like `arcs' in photoemission experiments.Comment: REVTeX 4, 5 pages, 4 EPS figures. References added; problem with figure 4 fixed; typos correcte

Spectral Properties of Correlated Materials: Local Vertex and Non-Local Two-Particle Correlations from Combined GW and Dynamical Mean Field Theory

We present a fully self-consistent combined GW and dynamical mean field (GW+DMFT) study of the spectral properties of the extended two-dimensional Hubbard model. The inclusion of the local dynamical vertex stemming from the DMFT self-energy and polarization is shown to cure the problems of self-consistent GW in the description of spectral properties. We calculate the momentum-resolved spectral functions, the two-particle polarization and electron loss spectra, and show that the inclusion of GW in extended DMFT leads to a narrowing of the quasi-particle width and more pronounced Hubbard bands in the metallic regime as one approaches the charge-ordering transition. Finally, the momentum-dependence introduced by GW into the extended DMFT description of collective modes is found to affect their shape, giving rise to dispersive plasmon-like long-wavelength and stripe modes.Comment: 5 pages, 4 figure

Spin-dependent Hedin's equations

Hedin's equations for the electron self-energy and the vertex were originally derived for a many-electron system with Coulomb interaction. In recent years it has been increasingly recognized that spin interactions can play a major role in determining physical properties of systems such as nanoscale magnets or of interfaces and surfaces. We derive a generalized set of Hedin's equations for quantum many-body systems containing spin interactions, e.g. spin-orbit and spin-spin interactions. The corresponding spin-dependent GW approximation is constructed.Comment: 5 pages, 1 figur

Low-energy models for correlated materials: bandwidth renormalization from Coulombic screening

We provide a prescription for constructing Hamiltonians representing the low energy physics of correlated electron materials with dynamically screened Coulomb interactions. The key feature is a renormalization of the hopping and hybridization parameters by the processes that lead to the dynamical screening. The renormalization is shown to be non-negligible for various classes of correlated electron materials. The bandwidth reduction effect is necessary for connecting models to materials behavior and for making quantitative predictions for low-energy properties of solids.Comment: 4 pages, 2 figure

Non-Fermi Liquid Behavior and Double-Exchange Physics in Orbital-Selective Mott Systems

We study a multi-band Hubbard model in its orbital selective Mott phase, in which localized electrons in a narrow band coexist with itinerant electrons in a wide band. The low-energy physics of this phase is shown to be closely related to that of a generalized double-exchange model. The high-temperature disordered phase thus differs from a Fermi liquid, and displays a finite scattering rate of the conduction electrons at the Fermi level, which depends continuously on the spin anisotropy.Comment: 5 pages, minor typos correcte

A supersymmetric model for triggering Supernova Ia in isolated white dwarfs

We propose a model for supernovae Ia explosions based on a phase transition to a supersymmetric state which becomes the active trigger for the deflagration starting the explosion in an isolated sub-Chandrasekhar white dwarf star. With two free parameters we fit the rate and several properties of type Ia supernovae and address the gap in the supermassive black hole mass distribution. One parameter is a critical density fit to about $3 \cdot 10^7$ g/cc while the other has the units of a space time volume and is found to be of order $0.05\,$ Gyr $R_E^3$ where $R_E$ is the earth radius. The model involves a phase transition to an exact supersymmetry in a small core of a dense star.Comment: 20 pages, 5 figures, expanded version to be published in Physical Review