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Abstracts
P1.23
Graphene-like microwave billiards: Van-Hove singularities (VHS)
and Excited-State Quantum Phase Transitions (ESQPT).
Macek, Michal(1) Iachello, Francesco(2) Dietz, Barbara(3, 4)
1) The Czech Academy of Sciences, Institute of Scientific Instruments,
Kralovopolska 147, 612 64 Brno, Czech Republic
2) Yale University, Center for Theoretical Physics, Sloane Physics Laboratory,
New Haven, Connecticut 06520-8120, USA
3) Technische Universitaet Darmstadt, Institut fuer Kernphysik, D-64289
Darmstadt, Germany
4) Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668
Warzawa, Poland
Superconducting 2D microwave resonators containing triangular lattices of
metallic cylinders form photonic crystals, which enable to model finite-sized
graphene flakes. High presision spectral measurements resolving all excitations
are possible. We describe the spectra by an algebraic model, providing analytical
solutions to the dispersion relations and density of states. At the VHS, whose
energies correspond to an ESQPT, we find stable stripe-like states parallel to the
zig-zag direction, simillar to the topological edge states, however these appear
in the bulk. They are stable with respect to long range perturbations and noise,
and appear also for irregular shapes of the boundaries.
P1.24
Localized excitations in 2D system of charged hard-core bosons
Yu.D. Panov(1), A.S. Moskvin(1), F.N. Rybakov(1,2), A.B. Borisov(1,2)
1) Ural Federal University, 620002, Mira str., 19, Ekaterinburg, Russia
2) Institute of Metal Physics UD RAS, 620990, S. Kovalevskaya str., 18,
Ekaterinburg, Russia
Making use of an asymptotic analysis and continual approximation we constructed
the phase diagram of localized excitations over a homogeneous ground state for
the 2D system of charged hard-core bosons. It is shown that in the superfluid
(SF) phase the excitations are the ferro- and antiferro- type vortices. Near the
boundary between the SF and supersolid (SS) phases, the antiferro-type vortices
in the SF phase begin to dominate, their inflation leads to a change of the
homogeneous ground state from the SF to SS phase. In the SS phase the vortices
are only possible at the half-filling (net charge-ordered phase), while at arbitrary
filling the topological excitations like skyrmions exist.
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