62,258 research outputs found
Phase dynamics of inductively coupled intrinsic Josephson junctions and terahertz electromagnetic radiation
The Josephson effects associated with quantum tunneling of Cooper pairs
manifest as nonlinear relations between the superconductivity phase difference
and the bias current and voltage. Many novel phenomena appear, such as Shapiro
steps in dc cuurent-voltage (IV) characteristics of a Josephson junction under
microwave shining, which can be used as a voltage standard. Inversely, the
Josephson effects provide a unique way to generate high-frequency
electromagnetic (EM) radiation by dc bias voltage. The discovery of cuprate
high-Tc superconductors accelerated the effort to develop novel source of EM
waves based on a stack of atomically dense-packed intrinsic Josephson junctions
(IJJs), since the large superconductivity gap covers the whole terahertz
frequency band. Very recently, strong and coherent terahertz radiations have
been successfully generated from a mesa structure of
single crystal which works both as the source
of energy gain and as the cavity for resonance. It is then found theoretically
that, due to huge inductive coupling of IJJs produced by the nanometer junction
separation and the large London penetration depth of order of of
the material, a novel dynamic state is stabilized in the coupled sine-Gordon
system, in which kinks in phase differences are developed responding
to the standing wave of Josephson plasma and are stacked alternatively in the
c-axis. This novel solution of the inductively coupled sine-Gordon equations
captures the important features of experimental observations. The theory
predicts an optimal radiation power larger than the one available to date by
orders of magnitude, and thus suggests the technological relevance of the
phenomena.Comment: review article (69 pages, 30 figures
Multipartite Entanglement Measures and Quantum Criticality from Matrix and Tensor Product States
We compute the multipartite entanglement measures such as the global
entanglement of various one- and two-dimensional quantum systems to probe the
quantum criticality based on the matrix and tensor product states (MPSs/TPSs).
We use infinite time-evolving block decimation (iTEBD) method to find the
ground states numerically in the form of MPSs/TPSs, and then evaluate their
entanglement measures by the method of tensor renormalization group (TRG). We
find these entanglement measures can characterize the quantum phase transitions
by their derivative discontinuity right at the critical points in all models
considered here. We also comment on the scaling behaviors of the entanglement
measures by the ideas of quantum state renormalization group transformations.Comment: 22 pages, 11 figure
A cryogenic surface-electrode elliptical ion trap for quantum simulation
Two-dimensional crystals of trapped ions are a promising system with which to
implement quantum simulations of challenging problems such as spin frustration.
Here, we present a design for a surface-electrode elliptical ion trap which
produces a 2-D ion crystal and is amenable to microfabrication, which would
enable higher simulated coupling rates, as well as interactions based on
magnetic forces generated by on-chip currents. Working in an 11 K cryogenic
environment, we experimentally verify to within 5% a numerical model of the
structure of ion crystals in the trap. We also explore the possibility of
implementing quantum simulation using magnetic forces, and calculate J-coupling
rates on the order of 10^3 / s for an ion crystal height of 10 microns, using a
current of 1 A
Effect of an InP/InGaAs Interface on Spin-orbit Interaction in InAlAs/InGaAs Heterostructures
We report the effect of the insertion of an InP/InGaAs
Interface on Rashba spin-orbit interaction in
InAlAs/InGaAs quantum wells. A small spin
split-off energy in InP produces a very intriguing band lineup in the valence
bands in this system. With or without this InP layer above the
InGaAs well, the overall values of the spin-orbit coupling
constant turned out to be enhanced or diminished for samples with the
front- or back-doping position, respectively. These experimental results, using
weak antilocalization analysis, are compared with the results of the
theory. The actual conditions of the interfaces and
materials should account for the quantitative difference in magnitude between
the measurements and calculations.Comment: Submitted for publication; v2 to adjust Eq.6; v3 to correct the
figure file name; v4, a revised version accepted for publication in Phys.
Rev.
Path integral for a relativistic Aharonov-Bohm-Coulomb system
The path integral for the relativistic spinless Aharonov-Bohm-Coulomb system
is solved, and the energy spectra are extracted from the resulting amplitude.Comment: 6 pages, Revte
A Spin-Isospin Dependent 3N Scattering Formalism in a 3D Faddeev Scheme
We have introduced a spin-isospin dependent three-dimensional approach for
formulation of the three-nucleon scattering. Faddeev equation is expressed in
terms of vector Jacobi momenta and spin-isospin quantum numbers of each
nucleon. Our formalism is based on connecting the transition amplitude to
momentum-helicity representations of the two-body -matrix and the deuteron
wave function. Finally the expressions for nucleon-deuteron elastic scattering
and full breakup process amplitudes are presented.Comment: 17 page
- …