TY  - JOUR
A1  - Di Sante, Domenico
A1  - Erdmenger, Johanna
A1  - Greiter, Martin
A1  - Matthaiakakis, Ioannis
A1  - Meyer, René
A1  - Fernandez, David Rodríguez
A1  - Thomale, Ronny
A1  - van Loon, Erik
A1  - Wehling, Tim
T1  - Turbulent hydrodynamics in strongly correlated Kagome metals
JF  - Nature Communications
N2  - 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.
KW  - coupling-constant dependence
KW  - shear viscosity
KW  - electron
KW  - resistance
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230380
VL  - 11
ER  - 
TY  - JOUR
A1  - Kim, N. Y.
A1  - Kusudo, K.
A1  - Löffler, A.
A1  - Höfling, S.
A1  - Forchel, A.
A1  - Yamamoto, Y.
T1  - Exciton-polariton condensates near the Dirac point in a triangular lattice
JF  - New Journal of Physics
N2  - Dirac particles, massless relativistic entities, obey linear energy dispersions and hold important implications in particle physics. The recent discovery of Dirac fermions in condensed matter systems including graphene and topological insulators has generated a great deal of interest in exploring the relativistic properties associated with Dirac physics in solid-state materials. In addition, there are stimulating research activities to engineer Dirac particles, elucidating their exotic physical properties in a controllable setting. One of the successful platforms is the ultracold atom-optical lattice system, whose dynamics can be manipulated and probed in a clean environment. A microcavity exciton-polariton-lattice system offers the advantage of forming high-orbital condensation in non-equilibrium conditions, which enables one to explore novel quantum orbital order in two dimensions. In this paper, we experimentally construct the band structures near Dirac points, the vertices of the first hexagonal Brillouin zone with exciton-polariton condensates trapped in a triangular lattice. Due to the finite spectral linewidth, the direct map of band structures at Dirac points is elusive; however, we identify the linear part above Dirac points and its associated velocity value is similar to ~0.9-2 x \(10^8 cm s^{-1}\), consistent with the theoretical estimate \(1 x 10^8 cm s^{-1}\) with a \(2 \mu m\) lattice constant. We envision that the exciton-polariton condensates in lattices would be a promising solid-state platform, where the system order parameter can be accessed in both real and momentum spaces.
KW  - Bose-Einstein condensation
KW  - carbon nanotubes
KW  - graphene
KW  - electron
KW  - dynamics
KW  - fermions
KW  - trap
KW  - gas
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-123103
SN  - 1367-2630
VL  - 15
IS  - 035032
ER  -