4,548 research outputs found
Strong-disorder renormalization for interacting non-Abelian anyon systems in two dimensions
We consider the effect of quenched spatial disorder on systems of
interacting, pinned non-Abelian anyons as might arise in disordered Hall
samples at filling fractions \nu=5/2 or \nu=12/5. In one spatial dimension,
such disordered anyon models have previously been shown to exhibit a hierarchy
of infinite randomness phases. Here, we address systems in two spatial
dimensions and report on the behavior of Ising and Fibonacci anyons under the
numerical strong-disorder renormalization group (SDRG). In order to manage the
topology-dependent interactions generated during the flow, we introduce a
planar approximation to the SDRG treatment. We characterize this planar
approximation by studying the flow of disordered hard-core bosons and the
transverse field Ising model, where it successfully reproduces the known
infinite randomness critical point with exponent \psi ~ 0.43. Our main
conclusion for disordered anyon models in two spatial dimensions is that
systems of Ising anyons as well as systems of Fibonacci anyons do not realize
infinite randomness phases, but flow back to weaker disorder under the
numerical SDRG treatment.Comment: 12 pages, 12 figures, 1 tabl
Two-dimensional quantum liquids from interacting non-Abelian anyons
A set of localized, non-Abelian anyons - such as vortices in a p_x + i p_y
superconductor or quasiholes in certain quantum Hall states - gives rise to a
macroscopic degeneracy. Such a degeneracy is split in the presence of
interactions between the anyons. Here we show that in two spatial dimensions
this splitting selects a unique collective state as ground state of the
interacting many-body system. This collective state can be a novel gapped
quantum liquid nucleated inside the original parent liquid (of which the anyons
are excitations). This physics is of relevance for any quantum Hall plateau
realizing a non-Abelian quantum Hall state when moving off the center of the
plateau.Comment: 5 pages, 6 figure
Temperature dependence of the diffuse scattering fine structure in equiatomic CuAu
The temperature dependence of the diffuse scattering fine structure from
disordered equiatomic CuAu was studied using {\it in situ} x-ray scattering. In
contrast to CuAu the diffuse peak splitting in CuAu was found to be
relatively insensitive to temperature. Consequently, no evidence for a
divergence of the antiphase length-scale at the transition temperature was
found. At all temperatures studied the peak splitting is smaller than the value
corresponding to the CuAuII modulated phase. An extended Ginzburg-Landau
approach is used to explain the temperature dependence of the diffuse peak
profiles in the ordering and modulation directions. The estimated mean-field
instability point is considerably lower than is the case for CuAu.Comment: 4 pages, 5 figure
On the relation between entanglement and subsystem Hamiltonians
We show that a proportionality between the entanglement Hamiltonian and the
Hamiltonian of a subsystem exists near the limit of maximal entanglement under
certain conditions. Away from that limit, solvable models show that the
coupling range differs in both quantities and allow to investigate the effect.Comment: 7 pages, 2 figures version2: minor changes, typos correcte
The continuum limit of the integrable open XYZ spin-1/2 chain
We show that the continuum limit of the integrable XYZ spin-1/2 chain on a
half-line gives rise to the boundary sine-Gordon theory using the perturbation
method.Comment: 8pages, LaTeX; typos in eq.(11) removed, one in reference correcte
Calibrating the Mixing Length Parameter for a Red Giant Envelope
Two-dimensional hydrodynamical simulations were made to calibrate the mixing
length parameter for modeling red giant's convective envelope. As was briefly
reported in Asida & Tuchman (97), a comparison of simulations starting with
models integrated with different values of the mixing length parameter, has
been made. In this paper more results are presented, including tests of the
spatial resolution and Large Eddy Simulation terms used by the numerical code.
The consistent value of the mixing length parameter was found to be 1.4, for a
red giant of mass 1.2 solar-mass, core mass of 0.96 solar-mass, luminosity of
200 solar-luminosities, and metallicity Z=0.001.Comment: 18 pages, 1 table, 13 figures. Accepted for publication in Ap.
Mode identification of Pulsating White Dwarfs using the HST
We have obtained time-resolved ultraviolet spectroscopy for the pulsating DAV
stars G226-29 and G185-32, and for the pulsating DBV star PG1351+489 with the
Hubble Space Telescope Faint Object Spectrograph, to compare the ultraviolet to
the optical pulsation amplitude and determine the pulsation indices. We find
that for essentially all observed pulsation modes, the amplitude rises to the
ultraviolet as the theoretical models predict for l=1 non-radial g-modes. We do
not find any pulsation mode visible only in the ultraviolet, nor any modes
whose phase flips by 180 degrees; in the ultraviolet, as would be expected if
high l pulsations were excited. We find one periodicity in the light curve of
G185-32, at 141 s, which does not fit theoretical models for the change of
amplitude with wavelength of g-mode pulsations.Comment: Accepted for publication in the Astrophysical Journal, Aug 200
Classification of topological insulators and superconductors in three spatial dimensions
We systematically study topological phases of insulators and superconductors
(SCs) in 3D. We find that there exist 3D topologically non-trivial insulators
or SCs in 5 out of 10 symmetry classes introduced by Altland and Zirnbauer
within the context of random matrix theory. One of these is the recently
introduced Z_2 topological insulator in the symplectic symmetry class. We show
there exist precisely 4 more topological insulators. For these systems, all of
which are time-reversal (TR) invariant in 3D, the space of insulating ground
states satisfying certain discrete symmetry properties is partitioned into
topological sectors that are separated by quantum phase transitions. 3 of the
above 5 topologically non-trivial phases can be realized as TR invariant SCs,
and in these the different topological sectors are characterized by an integer
winding number defined in momentum space. When such 3D topological insulators
are terminated by a 2D surface, they support a number (which may be an
arbitrary non-vanishing even number for singlet pairing) of Dirac fermion
(Majorana fermion when spin rotation symmetry is completely broken) surface
modes which remain gapless under arbitrary perturbations that preserve the
characteristic discrete symmetries. In particular, these surface modes
completely evade Anderson localization. These topological phases can be thought
of as 3D analogues of well known paired topological phases in 2D such as the
chiral p-wave SC. In the corresponding topologically non-trivial and
topologically trivial 3D phases, the wavefunctions exhibit markedly distinct
behavior. When an electromagnetic U(1) gauge field and fluctuations of the gap
functions are included in the dynamics, the SC phases with non-vanishing
winding number possess non-trivial topological ground state degeneracies.Comment: 20 pages. Changed title, added two table
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Deterministic positioning of nanophotonic waveguides around single self-assembled quantum dots
The capability to embed self-assembled quantum dots (QDs) at predefined positions in nanophotonic structures is key to the development of complex quantum-photonic architectures. Here, we demonstrate that QDs can be deterministically positioned in nanophotonic waveguides by pre-locating QDs relative to a global reference frame using micro-photoluminescence (μPL) spectroscopy. After nanofabrication, μPL images reveal misalignments between the central axis of the waveguide and the embedded QD of only (9 ± 46) nm and (1 ± 33) nm for QDs embedded in undoped and doped membranes, respectively. A priori knowledge of the QD positions allows us to study the spectral changes introduced by nanofabrication. We record average spectral shifts ranging from 0.1 nm to 1.1 nm, indicating that the fabrication-induced shifts can generally be compensated by electrical or thermal tuning of the QDs. Finally, we quantify the effects of the nanofabrication on the polarizability, the permanent dipole moment, and the emission frequency at vanishing electric field of different QD charge states, finding that these changes are constant down to QD-surface separations of only 70 nm. Consequently, our approach deterministically integrates QDs into nanophotonic waveguides whose light-fields contain nanoscale structure and whose group index varies at the nanometer level. © 2020 Author(s)
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