@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}
}
@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{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}
}