Dr. Jan Kuneš

Scientific Curriculum Vitae Jan Kuneš studied
physics at the Faculty of Mathematics and Physics of the
Charles University in Prague in
19921997. After a brief romance
with experimental physics at the
University of Salford, U.K. he persued
his postgradual studies with Dr. Pavel Novák at
the Institute of Physics of the Czech Academy of
Sciences in Prague and as a longterm visitor at the
Institute of Solid State and Materials Research in
Dresden. After finishing his PhD in 2002 he joined the
group of Prof. Warren Pickett at the University of
California Davis where he stayed till the fall of 2005.
In 2006 Kuneš joined the Center for Electronic
Correlations and Magnetism at the University of
Augsburg, Germany, supported by the Alexander von
Humboldt Research Fellowship (20062007) and continued
as a research associate.
In 2009 he was awarded the Purkyně Fellowship of the Czech Academy of Sciences. (cv) Kuneš's areas of research are computation of the electronic structure of materials using bandstrucutre methods (density functional theory), numerical manybody approaches to strong electronic correlations (dynamical meanfield theory, quantum MontoCarlo methods), relativistic effects (spinorbit coupling) and magnetism. 
Spin density distribution around Co atoms in the order phase of Pr_{0.5}Ca_{0.5}CoO_{3} obtained with LDA+U method. 
Excitonic
condensation in perovskite cobaltites Materials from the Pr_{0.5}Ca_{0.5}CoO_{3}
family exhibit a phase transition at
temperatures in the range 30120 K. The
transition is characterized by several
ordersofmagnitude increase of resistivity,
loss of Co local moment susceptibility and
valance crossover Pr^{3+} >Pr^{4+}.
We have performed LDA+U calculations which lead
to a ordered ground state characterized by
complicated order parameter, which describes
exciton condensation in spin triplet channel.
Phys. Rev. B 90, 235112 (2014) 
Various excitonic phases in twoband Hubbard model around half filling 
Excitonic
condensation of correlated electrons We have observed a new kind
of instability in materials close to the
spinstate transition. The instability leads to
formation of a condensate of spinful excitons.
The complex nature of the order parameter allows
several distinct thermodynamic phases already in
twoband model. When orbital degeneracies are
possible, e.g., in transition metal
perovskites with d6 configuration and even
richer physics described by a tensorial order
parameter arises. We have proposed some
materials and performed calculations with
solutions exhibiting the excitonic order.
Excitonic condensation of strongly correlated electrons (presentation pdf) 
Local spin susceptibility reflecting a twosublattice order at intermediate temperatures 
Electronic correlations in systems with
competing multiplets In
materials with strong electronic
correlations only a small number of atomic
states are visited during
quantummeachnical and statistical
evolution of the system. Typically
the belong to the lowest Nelectron
multiplet of the corresponding valence and
perhaps N+1 and N1 fluctuations around
this state. In some materials hower, two
(or more) multiplets may happen to have
comparable energies, which has profound
consequences. A prototypical examle is
LaCoO_{3}. We
use DMFT to investigate such systems both on
model and material specific level.
Susprising correlation effects in band insulators (presentation pdf) 
Spinup and down parts of the J=1/2 Wannier orbital 
Construction of Wannier orbitals with
wien2k We have
developed and interface between the
banstructre code wien2k and wannier90
software for calculation of so called
maximally localized Wannier orbitals. This
allows us to construct effective
Hamiltonians of materials. One of the
first applications includes Ir compounds
with strong spinorbit coupling where
spinprojection is no more a good quantum
number.
Comput. Phys. Commun. 181, 1888 (2010) 
Closing of the charge gap in MnO 
Simultaneous spin and Mott transition under
pressure MnO is a
prototypical Mott insulator, which
undergoes several transtions at high
pressure (~ 100 GPa): structural (NaCl
> NiAs structures), local moment
collapse (HS > LS transition), volume
collapse (within NiAs
structure), Mott transtition (insulator
> metal). Using
combination of LDA hamiltonian and
dynamical meanfield theory
(LDA+DMFTT approach) we study nature and
relationships of these transitions.
Hematite (Fe2O3) is isoelectronic to MnO
and exhibits similar behavoir
Crystalfield driven Mott transition in MnO under pressure (presentation pdf) 
Generalized bandstructure of NiO 
Dynamical meanfield (LDA+DMFT)
investigation of chargetransfer materials NiO is a
prominent example of so called chargetransfer
insulator (a subset of Mott insulators). To
describe the physics of chargetransfer
materials ligand state (oxygen pstate here)
must be explicitely included in the hamiltonian.
Using LDA+DMFT we study the singleparticle
spectra (PES, IBS, ARPES) of stociometric and
holedoped NiO.
NiO  hole doping and bandstructure of chargetransfer insulator (presentation pdf) 