2,873 research outputs found
Monolithic superconducting emitter of tunable circularly polarized terahertz radiation
We propose an approach to control the polarization of terahertz (THz)
radiation from intrinsic Josephson-junction stacks in single crystalline
high-temperature superconductor . By monolithically
controlling the surface current distributions in the truncated square mesa
structure, we can modulate the polarization of the emitted THz wave as a result
of two orthogonal fundamental modes excited inside the mesa. Highly polarized
circular terahertz waves with a degree of circular polarization of more than
99% can be generated using an electrically controlled method. The emitted
radiation has a high intensity and a low axial ratio (AR<1 dB). The intuitive
results obtained from the numerical simulation based on the conventional
antenna theory are consistent with the observed emission characteristics.Comment: Submitted to PRApplie
Polarization Enhancement of terahertz radiation generated by intrinsic Josephson junctions in a truncated edge square Bi_{2}Sr_{2}CaCu_{2}O_{8+{\delta}} mesa
In this study, we investigated the terahertz radiation from a truncated edge
square mesa structure made from a superconducting
Bi_{2}Sr_{2}CaCu_{2}O_{8+{\delta}} . Using a commercial software, the
polarization characteristics were determined, and introduced, while accounting
for the skin effect. The axial ratio was enhanced in the simulation by
performing a parametric study on the design.Comment: Proceedings of the 28th International Symposium on Superconductivity,
ISS 2015, November 16-18, 2015, Tokyo, Japa
Sums and products of ultracomplete topological spaces
AbstractIn 1987 V.I. Ponomarev and V.V. Tkachuk characterized strongly complete topological spaces as those spaces which have countable character in their Stone–Čech compactification. On the other hand, in 1998 S. Romaguera introduced the notion of cofinally Čech complete spaces and he showed that a metrizable space admits a cofinally complete metric (otherwise, called ultracomplete metric), a term introduced independently by N.R. Howes in 1971 and A. Császár in 1975, if and only if it is cofinally Čech complete. In a recent paper the authors showed that these two notions are equivalent and in this way answered a question raised by Ponomarev and Tkachuk [Vestnik MGU 5 (1987) 16–19] about giving an internal characterization for strongly complete topological spaces (termed ultracomplete by the authors). In this paper, sums and products of ultracomplete spaces are studied
Consequences of a possible adiabatic transition between \nu=1/3 and \nu=1 quantum Hall states in a narrow wire
We consider the possibility of creating an adiabatic transition through a
narrow neck, or point contact, between two different quantized Hall states that
have the same number of edge modes, such as \nu=1 and \nu=1/3. We apply both
the composite fermion and the Luttinger liquid formalism to analyze the
transition. We suggest that using such adiabatic junctions one could build a DC
step-up transformer, where the output voltage is higher than the input.
Difficulties standing in the way of an experimental implementation of the
adiabatic junction are addressed.Comment: 4 pages RevTex, includes 2 eps figures, Submitted to Phys. Rev. Let
Magnetoelasticity theory of incompressible quantum Hall liquids
A simple and physically transparent magnetoelasticity theory is proposed to
describe linear dynamics of incompressible fractional quantum Hall states. The
theory manifestly satisfies the Kohn theorem and the -sum rule, and predicts
a gaped intra-Landau level collective mode with a roton minimum. In the limit
of vanishing bare mass the correct form of the static structure factor,
, is recovered. We establish a connection of the present approach
to the fermionic Chern-Simons theory, and discuss further extensions and
applications. We also make an interesting analogy of the present theory to the
theory of visco-elastic fluids.Comment: RevTeX 4, 6 pages; expanded version to appear in PRB; more technical
details, and discussions of the physics adde
Flavor Symmetry Breaking and Vacuum Alignment on Orbifolds
Flavor symmetry has been widely studied for figuring out the masses and
mixing angles of standard-model fermions. In this paper we present a framework
for handling flavor symmetry breaking where the symmetry breaking is triggered
by boundary conditions of scalar fields in extra-dimensional space. The
alignment of scalar expectation values is achieved without referring to any
details of scalar potential and its minimization procedure. As applications to
non-abelian discrete flavor symmetries, illustrative lepton mass models are
constructed where the S3 and A4 flavor symmetries are broken down to the
directions leading to the tri-bimaximal form of lepton mixing and realistic
mass patterns.Comment: 21 page
Entropy and Exact Matrix Product Representation of the Laughlin Wave Function
An analytical expression for the von Neumann entropy of the Laughlin wave
function is obtained for any possible bipartition between the particles
described by this wave function, for filling fraction nu=1. Also, for filling
fraction nu=1/m, where m is an odd integer, an upper bound on this entropy is
exhibited. These results yield a bound on the smallest possible size of the
matrices for an exact representation of the Laughlin ansatz in terms of a
matrix product state. An analytical matrix product state representation of this
state is proposed in terms of representations of the Clifford algebra. For
nu=1, this representation is shown to be asymptotically optimal in the limit of
a large number of particles
Schwinger-Boson Mean-Field Theory of Mixed-Spin Antiferromagnet
The Schwinger-boson mean-field theory is used to study the three-dimensional
antiferromagnetic ordering and excitations in compounds , a large
family of quasi-one-dimensional mixed-spin antiferromagnet. To investigate
magnetic properties of these compounds, we introduce a three-dimensional
mixed-spin antiferromagnetic Heisenberg model based on experimental results for
the crystal structure of . This model can explain the experimental
discovery of coexistence of Haldane gap and antiferromagnetic long-range order
below N\'{e}el temperature. Properties such as the low-lying excitations,
magnetizations of and rare-earth ions, N\'{e}el temperatures of different
compounds, and the behavior of Haldane gap below the N\'{e}el temperature are
investigated within this model, and the results are in good agreement with
neutron scattering experiments.Comment: 12 pages, 6 figure
Temperature dependence of the conductivity of the electronic crystal
We study the temperature dependence of the conductivity of the 2D electronic
solid. In realistic samples, a domain structure forms in the solid and each
domain randomly orients in the absence of the in-plane field. At higher
temperature, the electron transport is governed by thermal activation form of
. The impurities will localize the
electron states along the edges of the crystal domains. At sufficient low
temperature, another transport mechanism called Mott's variable range hopping
mechanism, similar to that in a disorder insulator takes effect. We show that
as the temperature decreases, a crossover from the fixed range hopping of the
transport to the variable range hopping of transport in the 2D electron system
may be experimentally observed.Comment: 4 pages,1 figure
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