Past projects:

charge fluctuations
Charge fluctuations in Yb f-shell
Fluctuating vs intermediate valence - valence transition in Yb under pressure

The 4f shell of Yb can accomodate 13 or 14 electrons depending on a particular compound. This near degenracy of f13 and f14 valence states has deep consequences. Using LDA+DMFT we instigate continuous transition between the f13 and f14 valence states in elemental Yb induced by pressure and discuss it in terms of fluctuating and intermediate valence concepts.

Fluctuating valence and valence transition in Yb (presentation pdf)
pyrite structure
Pyrite crystal structure of NiS2
Metal-insulator transition in NiS2-xSex

The NiS2-xSex solid solution provides a model system where the trantion between metallic phase and the Mott insulator can be tuned by Se content, pressure or temperature. Using LDA+DMFT we show that, contrary to common claims, the transition is essentially controlled by varying hybridization gap  within the S(Se) p-band related to the bond length of the S-S (Se-Se) dimer.



Is NiS2 a charge-transfer insulator? (presentation pdf)
3d
Nesting function of compressed fcc Li

Superconductivity of  compressed fcc Li 

Discovery of higher temperature superconductivity in MgB2 brought about  a renewed interest in strongly coupled conventional superconductors.  Surprizingly  Li, one of the simplest possible  solids,  turns out to be  ~20 K superconductor when compressed.  We use  density functional electronic structure and linear response theory to investigate the origin of Li superconductivity and lattice dynamics and to link the effects to the Fermi surface topology.




Superconductivity and lattice instability of Li under pressure
(presentation pdf)

sigma
Change of inter-band conductivity below Tc
Electronic structure of EuB6
Presence of a gap in the bandstructure of EuB6 has been controversial for some time. We have studied the spectral weight transfer in the optical spectrum induced by magnetic ordering and conclude that the observed behavior is consistent only with a semimetallic groundstate.






Electronic structure of EuB6: insights from optical spectroscopy
(presentation pdf)