Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 25: Focussed session: Frontiers of electronic structure theory: Strong correlations from first principles II (jointly with TT)

O 25.8: Vortrag

Dienstag, 27. März 2012, 12:30–12:45, HE 101

Electronic properties of RbO₂ from DFT+DMFT calculations — •Roman Kovacik and Claude Ederer — School of Physics, Trinity College Dublin, Ireland

Recently, p-electron magnetism has received great attention as alternative option for spintronic applications. The “p-magnetism” is often defect-induced and systematic studies are hampered by poor reproducibility and wide spread in experimental data. It is therefore desirable to study intrinsic p-magnetism in pure bulk materials. We present results of a combined density functional theory + dynamical mean field theory (DFT+DMFT) study for RbO₂, an insulating antiferromagnet where magnetic properties arise from partially filled oxygen p orbitals. For the high-symmetry tetragonal structure, we calculate the Hamiltonian in the basis of maximally localized Wannier functions [1] with antibonding π^* character, which is then solved within DMFT using a continuous-time quantum Monte Carlo solver [2]. We construct a metal-insulator phase diagram as function of temperature and Hubbard interaction parameters U and J. For realistic values of U and J, we find that RbO₂ is a paramagnetic insulator at room temperature. We also find indications for orbital order at low temperatures (T≈30 K) in agreement with our previous DFT study [3]. Furthermore, we discuss differences between the realistic Hamiltonian and the one based on the semicircle density of states.
[1] I. Souza, N. Marzari, D. Vanderbilt, Phys. Rev. B 65, 035109 (2001).
E. Gull, A. J. Millis, et al., Rev. Mod. Phys. 83, 349 (2011).
R. Kováčik and C. Ederer, Phys. Rev. B 80, 140411(R) (2009).