Research projects
Superconducting quantum dots
Systems of interest: single-level quantum dots with local Coulomb interaction connected to metallic and superconducting (BCS) leads that can be described by the superconducting impurity Anderson model
Methods: second order perturbation theory in Coulomb interaction stregth, numerical renormalization group (NRG), CT-HYB quantum Monte Carlo
Goal: consistent description of the behavior of the subgap Andreev bound states (Yu-Shiba-Rusinov states) and the Josephson current in the vicinity of the single-doublet (zero-pi) quantum phase transitionRelated publications
P. Zalom, V. Pokorný, and T. Novotný, Phys. Rev. B 103, 035419 (2021).
V. Pokorný, M. Žonda, G. Loukeris, and T. Novotný, JPS Conf. Proc. 30, 011002 (2020).
A. Kadlecová, M. Žonda, V. Pokorný, and T. Novotný,
Phys. Rev. Applied 11, 044094 (2019).
V. Pokorný, M. Žonda, Physica B 536, 488 (2018).
T. Domański, M. Žonda, V. Pokorný, G. Górski, V. Janiš, and T. Novotný,
Phys. Rev. B 95, 045104 (2017).
V. Janiš, V. Pokorný, and M. Žonda, Eur. Phys. J. B 89, 197 (2016).
M. Žonda, V. Pokorný, V. Janiš, and T. Novotný, Phys. Rev. B 93, 024523 (2016).
M. Žonda, V. Pokorný, V. Janiš, and T. Novotný, Sci. Rep. 5, 8821 (2015).
Presentations
18. 6. 2019, IoP CAS, Prague, Czech Republic
3. 4. 2019, DPG Spring Meeting, Regensburg, Germany
12. 3. 2018, DPG Spring Meeting, Berlin, Germany
1. 1. 2018, Universität Regensburg, Germany
29. 11. 2016, IoP CAS, Prague, Czech Republic
24. 3. 2015, IoP CAS, Prague, Czech Republic
17. 10. 2014, IIASS, Vietri sul Mare (Salerno), ItalySoftware
SQUAD - SUperconducting QUAntum Dot - set of python scripts to calculate properties of these systems using the diagrammatic second order perturbation method
SQUAD-CTHYB - a TRIQS-based code to calculate properties of these systems using the CT-HYB quantum Monte-Carlo methodMolecular electronics
Systems of interest: spinful molecules attached to metallic or insulating substrates or leads
Methods: density functional theory (DFT), non-equilibrium Green functions (NEGF)
Goal: search for molecular systems suitable as building elements of molecular spintronic devicesRelated publications
H. Li et al, Angew. Chem. Int. Ed. 56 14145 (2017).Presentations
17. 2. 2020, Albert-Ludwigs-Universität Freiburg, Germany
2. 7. 2019, Prague, Czech Republic
20. 7. 2018, Universität Regensburg, Germany
Reseach group homepage
Computational theory of condensed matter groupThermodynamically consistent description of quantum criticality
We are developing methods based on diagrammatic perturbation techniques to study quantum criticality in interacting electron systems described by lattice models (e.g. Anderson or Hubbard model). Methods are based on the parquet construction of two-particle functions and provide a consistent description that is free of unphysical symmetry breaking and does not violate conservation laws.
Related publications
V. Janiš, A. Klíč, J. Yan, and V. Pokorný, Phys. Rev. B 102, 205120 (2020).
V. Janiš, P. Zalom, V. Pokorný, and A. Klíč, Phys. Rev. B 100, 195114 (2019).
V. Janiš, V. Pokorný, and A. Kauch, Phys. Rev. B 95, 165113 (2017).
V. Janiš, A. Kauch, and V. Pokorný, Phys. Rev. B 95, 045108 (2017).
Presentations
Poster from the 2017 summer school in Tallahassee (pdf)Software
SPEpy - Simplified Parquet Equations in python - set of python scripts to calculate properties of the single-impurity Anderson model using the simplified parquet equation solverCorrelated materials with strong spin-orbit interactions
We use the combination of ab-initio (LDA) methods and dynamical mean-field theory (DMFT) to study materials with strong effect of spin-orbit coupling on their electronic and magnetic properties. The focus lies on transition-metal oxides with heavy ions such as iridium and osmium. We use the continuous-time quantum Monte-Carlo method in the strong-coupling limit (CT-HYB) to solve the underlying impurity problem.
Related publications
K. Pajskr, P. Novák, V. Pokorný, J. Kolorenč, R. Arita, and J. Kuneš, Phys. Rev. B 93, 035129 (2016).Correlated electrons in disordered alloys (PhD thesis)
We developed methods to calculate charge transport in disordered systems of elastically scattered electrons. These diagrammatic methods are based on an asymptotic limit to high spatial dimensions and utilize advanced diagram summation techniques on the two-particle level. They allow us to calculate electrical conductivity and diffusion coefficient for arbitrary disorder strength. The numerical calculations are performed on the disordered Anderson model and the Falicov-Kimball model.
Related publications
V. Janiš and V. Pokorný, Phys. Rev. B 90, 045143 (2014).
V. Pokorný and V. Janiš, J. Phys.: Cond. Mat. 25, 175502 (2013).
V. Janiš and V. Pokorný, Ann. Phys. (Berlin) 523, 715 (2011).
V. Janiš and V. Pokorný, Phys. Rev. B 81, 165103 (2010).
PhD thesis (English, pdf, defended in 2013 at Charles University in Prague).Presentations
24. 4. 2012, IoP CAS, Prague, Czech Republic
14. 10. 2011, IIASS, Vietri sul Mare (Salerno), Italy
Critical properties of the mixed-spin Heisenberg model (Master thesis)
We studied the critical properties of the anisotropic mixed spin-1 and spin-1/2 quantum Heisenberg model using a simple two-site mean-field approximation. We treat in detail the system on the simple cubic lattice considering both exchange anisotropy and uniaxial singe-ion anisotropy. The critical behavior is analysed and the complete phase diagrams were calculated, where aside from the typical ferromagnetic phase a low-temperature quantum ordered phase is described.
Related publications
A. Bobák, V. Pokorný, and J. Dely, J. Phys.: Conf. Ser. 200, 022001 (2010).
A. Bobák, V. Pokorný, and J. Dely, Physica A 388, 2157 (2009).
Master thesis (Slovak, pdf, defended in 2008 at Pavol Jozef Šafárik University in Košice).Presentations
16. 12. 2008, IoP CAS, Prague, Czech Republic