TY  - JOUR
A1  - Elster, Lars
A1  - Platt, Christian
A1  - Thomale, Ronny
A1  - Hanke, Werner
A1  - Hankiewicz, Ewelina M.
T1  - Accessing topological superconductivity via a combined STM and renormalization group analysis
JF  - Nature Communications
N2  - The search for topological superconductors has recently become a key issue in condensed matter physics, because of their possible relevance to provide a platform for Majorana bound states, non-Abelian statistics, and quantum computing. Here we propose a new scheme which links as directly as possible the experimental search to a material-based microscopic theory for topological superconductivity. For this, the analysis of scanning tunnelling microscopy, which typically uses a phenomenological ansatz for the superconductor gap functions, is elevated to a theory, where a multi-orbital functional renormalization group analysis allows for an unbiased microscopic determination of the material-dependent pairing potentials. The combined approach is highlighted for paradigmatic hexagonal systems, such as doped graphene and water-intercalated sodium cobaltates, where lattice symmetry and electronic correlations yield a propensity for a chiral singlet topological superconductor. We demonstrate that our microscopic material-oriented procedure is necessary to uniquely resolve a topological superconductor state.
KW  - tunneling spectroscopy
KW  - Sr\(_2\)RuO\(_4\)
KW  - states
KW  - transition
KW  - insulators
KW  - surface
KW  - Majorana fermions
KW  - unconventional superconductivity
KW  - wave superconductors
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148181
VL  - 6
IS  - 8232
ER  - 
TY  - JOUR
A1  - Li, Gang
A1  - Yan, Binghai
A1  - Thomale, Ronny
A1  - Hanke, Werner
T1  - Topological nature and the multiple Dirac cones hidden in Bismuth high-Tc superconductors
JF  - Scientific Reports
N2  - Recent theoretical studies employing density-functional theory have predicted BaBiO\(_{3}\) (when doped with electrons) and YBiO\(_{3}\) to become a topological insulator (TI) with a large topological gap (~0.7 eV). This, together with the natural stability against surface oxidation, makes the Bismuth-Oxide family of special interest for possible applications in quantum information and spintronics. The central question, we study here, is whether the hole-doped Bismuth Oxides, i.e. Ba\(_{1-X}\)K\(_{X}\)BiO\(_{3}\) and BaPb\(_{1-X}\)Bi\(_{X}\)O\(_{3}\), which are "high-Tc" bulk superconducting near 30 K, additionally display in the further vicinity of their Fermi energy E\(_{F}\) a topological gap with a Dirac-type of topological surface state. Our electronic structure calculations predict the K-doped family to emerge as a TI, with a topological gap above E\(_{F}\). Thus, these compounds can become superconductors with hole-doping and potential TIs with additional electron doping. Furthermore, we predict the Bismuth-Oxide family to contain an additional Dirac cone below E\(_{F}\) for further hole doping, which manifests these systems to be candidates for both electron-and hole-doped topological insulators.
KW  - localized wannier functions
KW  - total energy calculations
KW  - phase transitions
KW  - insulator
KW  - BaPb\(_{1-X}\)Bi\(_{X}\)O\(_{3}\)
KW  - temperature
KW  - system
KW  - wave basis set
KW  - initio molecular dynamics
KW  - diffraction
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148569
VL  - 5
IS  - 10435
ER  - 
TY  - JOUR
A1  - Fleszar, Andrzej
A1  - Hanke, Werner
T1  - Two-dimensional metallicity with a large spin-orbit splitting: DFT calculations of the atomic, electronic, and spin structures of the Au/Ge(111)-(√3 x √3)R30° surface
JF  - Advances in Condensed Matter Physics
N2  - Density functional theory (DFT) is applied to study the atomic, electronic, and spin structures of the Au monolayer at the Ge(111) surface. It is found that the theoretically determined most stable atomic geometry is described by the conjugated honeycomb-chained-trimer (CHCT) model, in a very good agreement with experimental data. The calculated electronic structure of the system, being in qualitatively good agreement with the photoemission measurements, shows fingerprints of the many-body effects (self-interaction corrections) beyond the LDA or GGA approximations. The most interesting property of this surface system is the large spin splitting of its metallic surface bands and the undulating spin texture along the hexagonal Fermi contours, which highly resembles the spin texture at the Dirac state of the topological insulator Bi\(_{2}\)Te\(_{3}\). These properties make this system particularly interesting from both fundamental and technological points of view.
KW  - topological insulators
KW  - gas
KW  - density functional theory
KW  - conjugated honeycomb-chained-trimer
KW  - spin structures
KW  - Au/Ge(111)
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149221
VL  - 2015
IS  - 531498
ER  -