@article{LiYanThomaleetal.2015,
  author    = {Li, Gang and Yan, Binghai and Thomale, Ronny and Hanke, Werner},
  title     = {Topological nature and the multiple Dirac cones hidden in Bismuth high-Tc superconductors},
  series = {Scientific Reports},
  volume    = {5},
  journal   = {Scientific Reports},
  number    = {10435},
  doi       = {10.1038/srep10435},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148569},
  year      = {2015},
  abstract  = {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.},
  language  = {en}
}
@article{LeePapićThomale2015,
  author    = {Lee, Ching Hua and Papić, Zlatko and Thomale, Ronny},
  title     = {Geometric construction of quantum Hall clustering Hamiltonians},
  series = {Physical Review X},
  volume    = {5},
  journal   = {Physical Review X},
  number    = {4},
  doi       = {10.1103/PhysRevX.5.041003},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-145233},
  pages     = {041003},
  year      = {2015},
  abstract  = {Many fractional quantum Hall wave functions are known to be unique highest-density zero modes of certain "pseudopotential" Hamiltonians. While a systematic method to construct such parent Hamiltonians has been available for the infinite plane and sphere geometries, the generalization to manifolds where relative angular momentum is not an exact quantum number, i.e., the cylinder or torus, remains an open problem. This is particularly true for non-Abelian states, such as the Read-Rezayi series (in particular, the Moore-Read and Read-Rezayi Z\(_3\) states) and more exotic nonunitary (Haldane-Rezayi and Gaffnian) or irrational (Haffnian) states, whose parent Hamiltonians involve complicated many-body interactions. Here, we develop a universal geometric approach for constructing pseudopotential Hamiltonians that is applicable to all geometries. Our method straightforwardly generalizes to the multicomponent SU(n) cases with a combination of spin or pseudospin (layer, subband, or valley) degrees of freedom. We demonstrate the utility of our approach through several examples, some of which involve non-Abelian multicomponent states whose parent Hamiltonians were previously unknown, and we verify the results by numerically computing their entanglement properties.},
  language  = {en}
}
@article{RousochatzakisReutherThomaleetal.2015,
  author    = {Rousochatzakis, Ioannis and Reuther, Johannes and Thomale, Ronny and Rachel, Stephan and Perkins, N. B.},
  title     = {Phase Diagram and Quantum Order by Disorder in the Kitaev K\(_1\) - K\(_2\) Honeycomb Magnet},
  series = {Physical Review X},
  volume    = {5},
  journal   = {Physical Review X},
  number    = {041035},
  doi       = {10.1103/PhysRevX.5.041035},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-137235},
  year      = {2015},
  abstract  = {We show that the topological Kitaev spin liquid on the honeycomb lattice is extremely fragile against the second-neighbor Kitaev coupling K\(_2\), which has recently been shown to be the dominant perturbation away from the nearest-neighbor model in iridate Na\(_2\)IrO\(_3\), and may also play a role in \(\alpha\)-RuCl\(_3\) and Li\(_2\)IrO\(_3\). This coupling naturally explains the zigzag ordering (without introducing unrealistically large longer-range Heisenberg exchange terms) and the special entanglement between real and spin space observed recently in Na\(_2\)IrO\(_3\). Moreover, the minimal K\(_1\) - K\(_2\) model that we present here holds the unique property that the classical and quantum phase diagrams and their respective order-by-disorder mechanisms are qualitatively different due to the fundamentally different symmetries of the classical and quantum counterparts.},
  language  = {en}
}
@article{ElsterPlattThomaleetal.2015,
  author    = {Elster, Lars and Platt, Christian and Thomale, Ronny and Hanke, Werner and Hankiewicz, Ewelina M.},
  title     = {Accessing topological superconductivity via a combined STM and renormalization group analysis},
  series = {Nature Communications},
  volume    = {6},
  journal   = {Nature Communications},
  number    = {8232},
  doi       = {10.1038/ncomms9232},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148181},
  year      = {2015},
  abstract  = {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.},
  language  = {en}
}
@article{DuerrnagelBeyerThomaleetal.2022,
  author    = {D{\"u}rrnagel, Matteo and Beyer, Jacob and Thomale, Ronny and Schwemmer, Tilman},
  title     = {Unconventional superconductivity from weak coupling},
  series = {The European Physical Journal B},
  volume    = {95},
  journal   = {The European Physical Journal B},
  number    = {7},
  issn      = {1434-6028},
  doi       = {10.1140/epjb/s10051-022-00371-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-325153},
  year      = {2022},
  abstract  = {We develop a joint formalism and numerical framework for analyzing the superconducting instability of metals from a weak coupling perspective. This encompasses the Kohn-Luttinger formulation of weak coupling renormalization group for superconductivity as well as the random phase approximation imposed on the diagrammatic expansion of the two-particle Green's function. The central quantity to resolve is the effective interaction in the Cooper channel, for which we develop an optimized numerical framework. Our code is capable of treating generic multi-orbital models in two as well as three spatial dimensions and, in particular, arbitrary avenues of spin-orbit coupling.},
  language  = {en}
}
@article{LeeSutrisnoHofmannetal.2020,
  author    = {Lee, Ching Hua and Sutrisno, Amanda and Hofmann, Tobias and Helbig, Tobias and Liu, Yuhan and Ang, Yee Sin and Ang, Lay Kee and Zhang, Xiao and Greiter, Martin and Thomale, Ronny},
  title     = {Imaging nodal knots in momentum space through topolectrical circuits},
  series = {Nature Communications},
  volume    = {11},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-020-17716-1},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230407},
  year      = {2020},
  abstract  = {Knots are intricate structures that cannot be unambiguously distinguished with any single topological invariant. Momentum space knots, in particular, have been elusive due to their requisite finely tuned long-ranged hoppings. Even if constructed, probing their intricate linkages and topological "drumhead" surface states will be challenging due to the high precision needed. In this work, we overcome these practical and technical challenges with RLC circuits, transcending existing theoretical constructions which necessarily break reciprocity, by pairing nodal knots with their mirror image partners in a fully reciprocal setting. Our nodal knot circuits can be characterized with impedance measurements that resolve their drumhead states and image their 3D nodal structure. Doing so allows for reconstruction of the Seifert surface and hence knot topological invariants like the Alexander polynomial. We illustrate our approach with large-scale simulations of various nodal knots and an experiment which maps out the topological drumhead region of a Hopf-link. Topological phases with knotted configurations in momentum space have been challenging to realize. Here, Lee et al. provide a systematic design and measurement of a three-dimensional knotted nodal structure, and resolve its momentum space drumhead states via a topolectrical RLC-type circuit.},
  language  = {en}
}
@article{DiSanteErdmengerGreiteretal.2020,
  author    = {Di Sante, Domenico and Erdmenger, Johanna and Greiter, Martin and Matthaiakakis, Ioannis and Meyer, Ren{\´e} and Fernandez, David Rodr{\´i}guez and Thomale, Ronny and van Loon, Erik and Wehling, Tim},
  title     = {Turbulent hydrodynamics in strongly correlated Kagome metals},
  series = {Nature Communications},
  volume    = {11},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-020-17663-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230380},
  year      = {2020},
  abstract  = {A current challenge in condensed matter physics is the realization of strongly correlated, viscous electron fluids. These fluids can be described by holography, that is, by mapping them onto a weakly curved gravitational theory via gauge/gravity duality. The canonical system considered for realizations has been graphene. In this work, we show that Kagome systems with electron fillings adjusted to the Dirac nodes provide a much more compelling platform for realizations of viscous electron fluids, including non-linear effects such as turbulence. In particular, we find that in Scandium Herbertsmithite, the fine-structure constant, which measures the effective Coulomb interaction, is enhanced by a factor of about 3.2 as compared to graphene. We employ holography to estimate the ratio of the shear viscosity over the entropy density in Sc-Herbertsmithite, and find it about three times smaller than in graphene. These findings put the turbulent flow regime described by holography within the reach of experiments. Viscous electron fluids are predicted in strongly correlated systems but remain challenging to realize. Here, the authors predict enhanced effective Coulomb interaction and reduced ratio of the shear viscosity over entropy density in a Kagome metal, inferring turbulent flow of viscous electron fluids.},
  language  = {en}
}
@article{KremerBiesenthalMaczewskyetal.2019,
  author    = {Kremer, Mark and Biesenthal, Tobias and Maczewsky, Lukas J. and Heinrich, Matthias and Thomale, Ronny and Szameit, Alexander},
  title     = {Demonstration of a two-dimensional PT-symmetric crystal},
  series = {Nature Communications},
  volume    = {10},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-018-08104-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230132},
  year      = {2019},
  abstract  = {With the discovery of PT-symmetric quantum mechanics, it was shown that even non-Hermitian systems may exhibit entirely real eigenvalue spectra. This finding did not only change the perception of quantum mechanics itself, it also significantly influenced the field of photonics. By appropriately designing one-dimensional distributions of gain and loss, it was possible to experimentally verify some of the hallmark features of PT-symmetry using electromagnetic waves. Nevertheless, an experimental platform to study the impact of PT-symmetry in two spatial dimensions has so far remained elusive. We break new grounds by devising a two-dimensional PT-symmetric system based on photonic waveguide lattices with judiciously designed refractive index landscape and alternating loss. With this system at hand, we demonstrate a non-Hermitian two-dimensional topological phase transition that is closely linked to the emergence of topological mid-gap edge states.},
  language  = {en}
}
@article{LeeImhofBergeretal.2018,
  author    = {Lee, Ching Hua and Imhof, Stefan and Berger, Christian and Bayer, Florian and Brehm, Johannes and Molenkamp, Laurens W. and Kiessling, Tobias and Thomale, Ronny},
  title     = {Topolectrical Circuits},
  series = {Communications Physics},
  volume    = {1},
  journal   = {Communications Physics},
  doi       = {10.1038/s42005-018-0035-2},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236422},
  year      = {2018},
  abstract  = {Invented by Alessandro Volta and F{\´e}lix Savary in the early 19th century, circuits consisting of resistor, inductor and capacitor (RLC) components are omnipresent in modern technology. The behavior of an RLC circuit is governed by its circuit Laplacian, which is analogous to the Hamiltonian describing the energetics of a physical system. Here we show that topological insulating and semimetallic states can be realized in a periodic RLC circuit. Topological boundary resonances (TBRs) appear in the impedance read-out of a topolectrical circuit, providing a robust signal for the presence of topological admittance bands. For experimental illustration, we build the Su-Schrieffer-Heeger circuit, where our impedance measurement detects the TBR midgap state. Topolectrical circuits establish a bridge between electrical engineering and topological states of matter, where the accessibility, scalability, and operability of electronics synergizes with the intricate boundary properties of topological phases.},
  language  = {en}
}