The discovery of new high temperature superconductivity at the
beginning of March this year, generated tremendous interest in
condensed matter community, and a flurry of recent experimental and
theoretical activity. Exciting applications to superconducting cables,
were recently demonstrated.
In our recent preprint (Correlated electronic
structure of LaOFeAs) , we were the first to point out that
phonons can not explain high superconducting transition temperatures
found in the iron oxypnictides. We predicted the band structure and
optical conductivity of the correlated metal, LaOFeAs, the parent
compound of the new high-Tc's.
In the second preprint
(Coherence-incoherence crossover in the normal state of iron-oxypnictides and importance of the Hund's rule coupling)
we addressed the normal state properties of the doped compound, and
explained where do the magnetic moments come from, and why is the
material correlated. We predicted resistivity, magnetic
susceptibility, and specific heat of the doped compound. The Hund's
coupling was estimated to be 0.35-0.4eV.
Here are some links to hot papers on FeAs superconductors .
report we address the fundamental question of crossover from localized
to itinerant state of a paradigmatic heavy fermion material
CeIrIn5. The temperature evolution of the one electron
spectra and the optical conductivity is predicted from first
principles calculation. The buildup of coherence in the form of a
dispersive many body feature is followed in detail and its effects
on the conduction electrons of the material is revealed. We find
multiple hybridization gaps and link them to the crystal structure
of the material. Our theoretical approach explains the multiple peak structures
observed in optical experiments and the sensitivity
of CeIrIn5 to substitutions of the transition metal
element and may provide a microscopic basis for the more
phenomenological descriptions currently used to interpret
experiments in heavy fermion systems.
In this Nature letter, we
explain the unique nature of plutonium delta phase, namely its mixed
valence nature, and contrast it to curium metallic phase where f
electrons are localized and order antiferromagneticaly at low
temperature. Curium follows americium in periodic table and is thus
kind of analog of plutonium: plutonium has one hole in americium inert
f-shell (J=0) while curium has one more electron in the americium
inert shell. The striking different properties of the two elements
(one mixed valent non magnetic and other magnetic with Tc=65K) was
hard to understand with any band structure method. We developed
accurate Dynamical Mean-Field Method in combination with LDA and
showed that it describes from first principles the peculiarities of
the two materials. This method is the first that described magnetism
at finite temperature from first principles and show that plutonium is
non-magnetic while curium orders below 100K. This method holds a
great promise that it could predict magnetism from first principles.