2,481 research outputs found
Symmetry Reduction and Boundary Modes for Fe-Chains on an s-wave Superconductor
We investigate the superconducting phase diagram and boundary modes for a
quasi-1D system formed by three Fe-Chains on an s-wave superconductor,
motivated by the recent Princeton experiment. The onsite
spin-orbit term, inter-chain diagonal hopping couplings, and magnetic disorders
in the Fe-chains are shown to be crucial for the superconducting phases, which
can be topologically trivial or nontrivial in different parameter regimes. For
the topological regime a single Majorana and multiple Andreew bound modes are
obtained in the ends of the chain, while for the trivial phase only low-energy
Andreev bound states survive. Nontrivial symmetry reduction mechanism induced
by the term, diagonal hopping couplings, and magnetic
disorder is uncovered to interpret the present results. Our study also implies
that the zero-bias peak observed in the recent experiment may or may not
reflect the Majorana zero modes in the end of the Fe-chains.Comment: 5 pages, 4 figures; some minor errors are correcte
How volatilities nonlocal in time affect the price dynamics in complex financial systems
What is the dominating mechanism of the price dynamics in financial systems
is of great interest to scientists. The problem whether and how volatilities
affect the price movement draws much attention. Although many efforts have been
made, it remains challenging. Physicists usually apply the concepts and methods
in statistical physics, such as temporal correlation functions, to study
financial dynamics. However, the usual volatility-return correlation function,
which is local in time, typically fluctuates around zero. Here we construct
dynamic observables nonlocal in time to explore the volatility-return
correlation, based on the empirical data of hundreds of individual stocks and
25 stock market indices in different countries. Strikingly, the correlation is
discovered to be non-zero, with an amplitude of a few percent and a duration of
over two weeks. This result provides compelling evidence that past volatilities
nonlocal in time affect future returns. Further, we introduce an agent-based
model with a novel mechanism, that is, the asymmetric trading preference in
volatile and stable markets, to understand the microscopic origin of the
volatility-return correlation nonlocal in time.Comment: 16 pages, 7 figure
Fantastic Behavior of High-TC Superconductor Junctions: Tunable Superconductivity
Carrier injection performed in oxygen-deficient YBa2Cu3O7(YBCO)
hetero-structure junctions exhibited tunable resistance that was entirely
different with behaviors of semiconductor devices. Tunable superconductivity in
YBCO junctions, increasing over 20 K in transition temperature, has achieved by
using electric processes. To our knowledge, this is the first observation that
intrinsic property of high TC superconductors superconductivity can be adjusted
as tunable functional parameters of devices. The fantastic phenomenon caused by
carrier injection was discussed based on a proposed charge carrier
self-trapping model and BCS theory.Comment: 5 pages, 4 figure
A convenient look-up-table based method for the compensation of non-linear error in digital fringe projection
AbstractAlthough the structured light system that uses digital fringe projection has been widely implemented in three-dimensional surface profile measurement, the measurement system is susceptible to non-linear error. In this work, we propose a convenient look-up-table-based (LUT-based) method to compensate for the non-linear error in captured fringe patterns. Without extra calibration, this LUT-based method completely utilizes the captured fringe pattern by recording the full-field differences. Then, a phase compensation map is established to revise the measured phase. Experimental results demonstrate that this method works effectively
Optically-Nonactive Assorted Helices Array with Interchangeable Magnetic/Electric Resonance
We report here the designing of optically-nonactive metamaterial by
assembling metallic helices with different chirality. With linearly polarized
incident light, pure electric or magnetic resonance can be selectively
realized, which leads to negative permittivity or negative permeability
accordingly. Further, we show that pure electric or magnetic resonance can be
interchanged at the same frequency band by merely changing the polarization of
incident light for 90 degrees. This design demonstrates a unique approach to
construct metamaterial.Comment: 15 pages, 4 figure
Tip induced unconventional superconductivity on Weyl semimetal TaAs
Weyl fermion is a massless Dirac fermion with definite chirality, which has
been long pursued since 1929. Though it has not been observed as a fundamental
particle in nature, Weyl fermion can be realized as low-energy excitation
around Weyl point in Weyl semimetal, which possesses Weyl fermion cones in the
bulk and nontrivial Fermi arc states on the surface. As a firstly discovered
Weyl semimetal, TaAs crystal possesses 12 pairs of Weyl points in the momentum
space, which are topologically protected against small perturbations. Here, we
report for the first time the tip induced superconductivity on TaAs crystal by
point contact spectroscopy. A conductance plateau and sharp double dips are
observed in the point contact spectra, indicating p-wave like unconventional
superconductivity. Furthermore, the zero bias conductance peak in low
temperature regime is detected, suggesting potentially the existence of
Majorana zero modes. The experimentally observed tunneling spectra can be
interpreted with a novel mirror-symmetry protected topological superconductor
induced in TaAs, which can exhibit zero bias and double finite bias peaks, and
double conductance dips in the measurements. Our work can open a broad avenue
in search for new topological superconducting phases from topological Weyl
materials and trigger intensive investigations for pursuing Majorana fermions
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