Browsing by Subject "DFT"
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- Research DataA j_eff 12 Kitaev material on the triangular lattice: The case of NaRuO22023-06-07Motivated by recent reports of a quantum disordered ground state in the triangular lattice compound NaRuO$_2$, we derive a $j_{\rm eff}=1/2$ magnetic model for this system by means of first-principles calculations. The pseudospin Hamiltonian is dominated by bond-dependent off-diagonal $\Gamma$ interactions, complemented by a ferromagnetic Heisenberg exchange and a notably \emph{antiferromagnetic} Kitaev term. In addition to bilinear interactions, we find a sizable four-spin ring exchange contribution with a \emph{strongly anisotropic} character, which has been so far overlooked when modeling Kitaev materials. The analysis of the magnetic model, based on the minimization of the classical energy and exact diagonalization of the quantum Hamiltonian, points toward the existence of a rather robust easy-plane ferromagnetic order, which cannot be easily destabilized by physically relevant perturbations.
354 39 - Research DataAb initio study of highly tunable charge transfer in β-RuCl3/graphene heterostructures2024-06-25Heterostructures of graphene in proximity to magnetic insulators open the possibility to investigate exotic states emerging from the interplay of magnetism, strain and charge transfer between the layers. Recent reports on the growth of self-integrated atomic wires of $\beta$-RuCl$_3$ on graphite suggest these materials as versatile candidates to investigate these effects. Here we present detailed first principles calculations on the charge transfer and electronic structure of $\beta$-RuCl$_3$/graphene heterostructures and provide a comparison with the work function analysis of the related honeycomb family members $\alpha$-RuX$_3$ (X = Cl,Br,I). We find that proximity of the two layers leads to a hole-doped graphene and electron-doped RuX$_3$ in all cases, which is sensitively dependent on the distance between the two layers. Furthermore, strain effects due to lattice mismatch control the magnetization which itself has a strong effect on the charge transfer. Charge accumulation in $\beta$-RuCl$_3$ strongly drops away from the chain making such heterostructures suitable candidates for sharp interfacial junctions in graphene-based devices.
48 1 - Research DataData for: Influence of magnetism, strain and pressure on the band topology of EuCd2As22023-11-08Motivated by the wealth of proposals and realizations of nontrivial topological phases in EuCd2As2, such as a Weyl semimetallic state and the recently discussed semimetallic versus semiconductor behavior in this system, we analyze in this work the role of the delicate interplay of Eu magnetism, strain and pressure on the realization of such phases. For that we invoke a combination of a group theoretical analysis with ab initio density functional theory calculations and uncover a rich phase diagram with various non-trivial topological phases beyond a Weyl semimetallic state, such as axion and topological crystalline insulating phases, and discuss their realization.
36 4 - Research DataMicroscopic analysis of the valence transition in tetragonal EuPd2Si22023-02-23Under temperature or pressure tuning, tetragonal EuPd2Si2 is known to undergo a valence transition from nearly divalent to nearly trivalent Eu accompanied by a volume reduction. Albeit intensive work, its microscopic origin is still being discussed. Here, we investigate the mechanism of the valence transition under volume compression by ab initio density functional theory (DFT) calculations. Our analysis of the electronic and magnetic properties of EuPd2Si2 when approaching the valence transition shows an enhanced c−f hybridization between localized Eu 4f states and itinerant conduction states (Eu 5d, Pd 4d, and Si 3p) where an electronic charge redistribution takes place. We observe that the change in the electronic structure is intimately related to the volume reduction where Eu-Pd(Si) bond lengths shorten and, for the transition to happen, we trace the delicate balance between electronic bandwidth, crystal field splitting, Coulomb repulsion, Hund's coupling and spin-orbit coupling. In a next step we compare and benchmark our DFT results to surface-sensitive photoemission data in which the mixed-valent properties of EuPd2Si2 are reflected in a simultaneous observation of divalent and trivalent signals from the Eu 4f shell. The study serves as well to explore the limits of density functional theory and the choice of exchange correlation functionals to describe such a phenomenon as a valence transition.
30 4 - Research DataTheoretical data for: Orbital occupancy and hybridization in strained SrVO3 epitaxial films2021-09-09These data were produced for an experimental paper of M. Mirjolet [1]. To generate them we used the density functional theory FPLO [2]. This gave us the integrated density of states, with whom we combined the different orbitals and atoms to obtain the results depicted in the publication [1]. The data of the post processing part are the data given in this upload. To reproduce the density functional part one needs to repeat the calculation. The input parameters are given in the publication [1]. For further information on the experimental data, please contact: mathieu.mirjolet@gmail.com. [1] M. Mirjolet et al. Phys. Rev. Mater. 5, 095002 (2021) [2] https://www.fplo.de/
93 5 - Research DataTheory data for: Tuning superconductivity and spin-vortex instabilities in CaKFe4As4 through in-plane antisymmetric strains CaKFe 4 As 4 through in-plane antisymmetric strains2024-05-13Here we present the data for "Tuning superconductivity and spin-vortex instabilities in CaKFe4As4 through in-plane antisymmetric strains CaKFe 4 As 4 through in-plane antisymmetric strains". Given are the SCF input files, and the first ouput file. To obtain the full data with charge densities one can rerun the calculations. It is split to the magnetic orders: hedgehog, and stripe order. Each order has the subdirectories for ground state and strain. The ground state case was used to get a first preconverged charge densities. All other runs are based on this charge density. The strain directories contain two further subdirectory for the type of strain. One is diagonal the other one along the a axis. For both strain cases four different strain values where calculated.
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