Tom Berlijn

Relevance of the Heisenberg-Kitaev model for the honeycomb lattice iridates A2IrO3.

Combining thermodynamic measurements with theoretical calculations we demonstrate that the iridates A2IrO3 (A=Na, Li) are magnetically ordered Mott insulators where the magnetism of the effective spin-orbital S=1/2 moments can be captured by a Heisenberg-Kitaev (HK) model with interactions beyond nearest-neighbor exchange. Experimentally, we observe an increase of the Curie-Weiss temperature from θ≈-125  K for Na2IrO3 to θ≈-33  K for Li2IrO3, while the ordering temperature remains roughly the same T(N)≈15  K. Using functional renormalization group calculations we show that this evolution of θ and T(N) as well as the low temperature zigzag magnetic order can be captured within this extended HK model. We estimate that Na2IrO3 is deep in a magnetically ordered regime, while Li2IrO3 appears to be close to a spin-liquid regime.

Unfolding first-principles band structures.

A general method is presented to unfold band structures of first-principles supercell calculations with proper spectral weight, allowing easier visualization of the electronic structure and the degree of broken translational symmetry. The resulting unfolded band structures contain additional rich information from the Kohn-Sham orbitals, and absorb the structure factor that makes them ideal for a direct comparison with angle resolved photoemission spectroscopy experiments. With negligible computational expense via the use of Wannier functions, this simple method has great practical value in the studies of a wide range of materials containing impurities, vacancies, lattice distortions, or spontaneous long-range orders.

Long-range magnetic ordering in Na2IrO3

We report a combined experimental and theoretical investigation of the magnetic structure of the honeycomb-lattice magnet Na

Do transition-metal substitutions dope carriers in iron-based superconductors?

{}_{2}

Enhanced superconductivity due to forward scattering in FeSe thin films on SrTiO3 substrates

IrO

One-Fe versus two-Fe Brillouin zone of Fe-based superconductors: creation of the electron pockets by translational symmetry breaking.

{}_{3}

Recovering hidden Bloch character: Unfolding electrons, phonons, and slabs

, a candidate for a realization of a gapless spin liquid. Using resonant x-ray magnetic scattering at the Ir

Effective doping and suppression of Fermi surface reconstruction via Fe vacancy disorder in K

{\mathrm{L}}_{3}

_x

edge, we find three-dimensional long-range antiferromagnetic order below

Fe

{T}_{N}=13.3