Biomedical subjects

Gabriel Kotliar

Publications and source records attributed to Gabriel Kotliar.

6 recordsLinked to original sources

PubMed2006

Many-body electronic structure of americium metal.

We report computer based simulations of energetics, spectroscopy, and electron-phonon interaction of americium using a novel spectral density functional method. This approach gives rise to a new concept of a many-body electronic structure and reveals the unexpected mixed valence regime of Am 5f6 electrons which under pressure acquire the 5f7 valence state. This explains the unique properties of Am and addresses the fundamental issue of how the localization delocalization edge is approached from the localized side in a closed shell system.

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PubMed2005

Understanding the heavy fermion phenomenology from a microscopic model.

We solve the 3D periodic Anderson model using a two impurity cluster dynamical mean field theory. We obtain the temperature versus hybridization phase diagram. Approaching the quantum critical point (QCP) both the Néel and lattice Kondo temperatures decrease and they do not cross at the lowest temperature we reached. While strong ferromagnetic spin fluctuation on the Kondo side is observed, our result suggests the critical static spin susceptibility is local in space at the QCP. We observe in the crossover region a logarithmic temperature dependence in the specific heat coefficient and spin susceptibility.

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PubMed2005

The alpha--> gamma transition in Ce: a theoretical view from optical spectroscopy.

Using a novel approach to calculate optical properties of strongly correlated systems, we address the old question of the physical origin of the alpha--> gamma transition in Ce. We find that the Kondo collapse model, involving both the f and the spd electrons, describes the optical data better than a Mott transition picture involving the f electrons only. Our results compare well with existing experiments on thin films. We predict the full temperature dependence of the optical spectra and find the development of a hybridization pseudogap in the vicinity of the alpha--> gamma phase transition.

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PubMed2004

Many-body approximation scheme beyond GW.

We explore the combination of the extended dynamical mean field theory (EDMFT) with the GW approximation (GWA); the former sums the local contributions to the self-energies to infinite order in closed form and the latter handles the nonlocal ones to lowest order. We investigate the different levels of self-consistency that can be implemented within this method by comparing to the exact quantum Monte Carlo solution of a finite-size model Hamiltonian. We find that using the EDMFT solution for the local self-energies as input to the GWA for the nonlocal self-energies gives the best result.

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PubMed2003

Physics. Driving the electron over the edge.

At low temperatures, many materials, from organics to oxides, undergo a pressure-driven "Mott transition": A small change in the distance between the atoms causes the electrical resistivity of the system to change by many orders of magnitude, without a change in crystal symmetry. In his Perspective, Kotliar highlights the report by Limelette et al., who have investigated the dependence of the resistivity of a doped vanadium oxide on pressure and temperature around the Mott critical endpoint (where the Mott transition becomes continuous). A purely electronic model accounts for the major features of the experiments, but some more detailed features require the coupling between electrons and the crystal lattice to be taken into account.

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PubMed2003

Extended dynamical mean field theory study of the periodic Anderson model.

We investigate the competition of the Kondo and the RKKY interactions in heavy fermion systems. We solve a periodic Anderson model using extended dynamical mean field theory (EDMFT) with quantum Monte Carlo method. We monitor simultaneously the evolution of the electronic and magnetic properties. As the RKKY coupling increases the heavy fermion quasiparticle unbinds and a local moment forms. At a critical RKKY coupling there is an onset of magnetic order. Within EDMFT the two transitions occur at different points and the disappearance of the magnetism is not described by a local quantum critical point.

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