Dr. Jan Kuneš

e-mail: kunes(at)fzu.cz
tel: +420 266 052 771
Institute of Physics
Academy of Sciences
Na Slovance 1999/2
Praha 8 182 21

List of publications
Conferences and presentations
Press coverage


Scientific Curriculum Vitae
Jan Kuneš studied physics at the Faculty of Mathematics and Physics of the Charles University in Prague  in  1992-1997.  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 long-term 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 (2006-2007) 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 many-body approaches to strong electronic correlations (dynamical mean-field theory, quantum Monto-Carlo methods), relativistic effects (spin-orbit coupling) and magnetism.

  ERC Consolidator grant 2014


  2015 APS outstanding referee      

Recent projects

spin density
Spin density distribution around Co atoms in the order phase of  Pr0.5Ca0.5CoO3 obtained with LDA+U method.
Excitonic condensation in perovskite cobaltites

Materials from the Pr0.5Ca0.5CoO3 family exhibit a phase transition at temperatures in the range 30-120 K. The transition is characterized by several orders-of-magnitude increase of resistivity, loss of Co local moment susceptibility and valance crossover Pr3+ ->Pr4+. 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)
phase diagram
Various excitonic phases in two-band Hubbard model around half filling
Excitonic condensation of correlated electrons

We have observed a new kind of instability in materials close to the spin-state 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 two-band 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 two-sublattice 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 quantum-meachnical and statistical evolution of the  system. Typically the belong to the lowest N-electron multiplet of the corresponding valence and perhaps N+1 and N-1 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 LaCoO3. We use DMFT to investigate such systems both on model and material specific level.

Susprising correlation effects in band insulators (presentation pdf)
Wannier function
Spin-up 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 spin-orbit coupling where spin-projection 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 mean-field theory (LDA+DMFTT approach) we study nature and relationships of these transitions. Hematite (Fe2O3) is isoelectronic to MnO and exhibits similar behavoir

Crystal-field driven Mott transition in MnO
under pressure (presentation pdf)

NiO bands
Generalized bandstructure of NiO
Dynamical  mean-field  (LDA+DMFT) investigation
of charge-transfer materials

NiO is a prominent example of so called charge-transfer insulator (a subset of Mott insulators). To describe the physics of charge-transfer materials ligand state (oxygen p-state here) must be explicitely included in the hamiltonian. Using LDA+DMFT we study the single-particle spectra (PES, IBS, ARPES) of stociometric and hole-doped NiO.

NiO - hole doping and bandstructure of charge-transfer
insulator (presentation pdf)

Older projects