2,574 research outputs found
Holographic topological defects in a ring: role of diverse boundary conditions
We investigate the formation of topological defects in the course of a
dynamical phase transition with different boundary conditions in a ring from
AdS/CFT correspondence. According to the Kibble-Zurek mechanism, quenching the
system across the critical point to symmetry-breaking phase will result in
topological defects -- winding numbers -- in a compact ring. By setting two
different boundary conditions, i.e., Dirichlet and Neumann boundary conditions
for the spatial component of the gauge fields in the AdS boundary, we achieve
the holographic superfluid and holographic superconductor models, respectively.
In the final equilibrium state, different configurations of the order parameter
phases for these two models indicate a persistent superflow in the holographic
superfluid, however, the holographic superconductor lacks this superflow due to
the existence of local gauge fields. The two-point correlation functions of the
order parameter also behave differently. In particular, for holographic
superfluid the correlation function is a cosine function depending on the
winding number. The correlation function for the holographic superconductor,
however, decays rapidly at short distances and vanishes at long distance, due
to the random localities of the gauge fields. These results are consistent with
our theoretical analysis.Comment: 15pages, 4 figures; Contexts improved and references added; Accepted
by JHE
Parity Symmetry Breaking and Kink Hairy Black Hole
Motivated by the Kibble-Zurek mechanism and the Gubser's argument for the
charged scalar hairs near the black hole horizon in a spacetime with negative
cosmological constant, we realize the kink hairs in a planar Schwarzschild-AdS
black hole. By increasing the chemical potential across the critical point of
the dual boundary field theory, the former symmetry of the real scalar
fields spontaneously break and form kinks in the bulk. Correspondingly, in the
AdS boundary it resembles the kinks in a one-dimensional chain. The relation
between the kink numbers and the quench rate obeys a universal scaling law
which satisfies the Kibble-Zurek's prediction.Comment: 10 pages; 3 figure
Electronic band gaps and transport in aperiodic graphene superlattices of Thue-Morse sequence
We have studied the electronic properties in aperiodic graphene superlattices
of Thue-Morse sequence. Although the structure is aperiodic, an unusual Dirac
point (DP) does exist and its location is exactly at the position of the
zero-averaged wave number (zero-. Furthermore, the zero- gap
associated with the DP is robust against the lattice constants and the incident
angles, and multi-DPs can appear under the suitable conditions. A resultant
controllability of electron transport in Thue-Morse sequence is predicted,
which may facilitate the development of many graphene-based electronics.Comment: Accepted for publication in Applied Physics Letters; 4 pagese, 5
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