11,846 research outputs found
Bond distortion effects and electric orders in spiral multiferroic magnets
We study in this paper bond distortion effect on electric polarization in
spiral multiferroic magnets based on cluster and chain models. The bond
distortion break inversion symmetry and modify the - hybridization.
Consequently, it will affect electric polarization which can be divided into
spin-current part and lattice-mediated part. The spin-current polarization can
be written in terms of and
the lattice-mediated polarization exists only when the M-O-M bond is distorted.
The electric polarization for three-atom M-O-M and four-atom M-O-M
clusters is calculated. We also study possible electric ordering in three kinds
of chains made of different clusters. We apply our theory to multiferroics
cuprates and find that the results are in agreement with experimental
observations.Comment: 14 pages, 11 figure
Extreme spin squeezing from deep reinforcement learning
Spin squeezing (SS) is a recognized resource for realizing measurement precision beyond the standard quantum limit proportional to 1/root N. The rudimentary one-axis twisting (OAT) interaction can facilitate SS and has been realized in diverse experiments, but it cannot achieve extreme SS for precision at the Heisenberg limit a proportional to 1/N. Aided by deep reinforcement learning (DRL), we discover size-independent universal rules for realizing nearly extreme SS with a OAT interaction using merely a handful of rotation pulses. More specifically, only six pairs of pulses are required for up to 10(4) particles, while the time taken to reach extreme SS remains on the same order of the optimal OAT squeezing time, which makes our scheme viable for experiments that reported OAT squeezing. This Rapid Communication highlights the potential of DRL for controlled quantum dynamics
Suppression of the superconducting energy gap in intrinsic Josephson junctions of single crystals
We have observed back-bending structures at high bias current in the
current-voltage curves of intrinsic Josephson junctions. These structures may
be caused by nonequilibrium quasiparticle injection and/or Joule heating. The
energy gap suppression varies considerably with temperature. Different levels
of the suppression are observed when the same level of current passes through
top electrodes of different sizes. Another effect which is seen and discussed,
is a super-current ``reentrance'' of a single intrinsic Josephson junction with
high bias current.Comment: accepted by Supercond. Sci. and Tech., 200
Coexistence of Ferroelectric Triclinic Phases and Origin of Large Piezoelectric Responses in Highly Strained BiFeO3 films
The structural evolution of the strain-driven morphotropic phase boundary
(MPB) in BiFeO3 films has been investigated using synchrotron x-ray
diffractometry in conjunction with scanning probe microscopy. Our results
demonstrate the existence of mixed-phase regions that are mainly made up of two
heavily tilted ferroelectric triclinic phases. Analysis of first-principles
computations suggests that these two triclinic phases originate from a phase
separation of a single monoclinic state accompanied by elastic matching between
the phase-separated states. These first-principle calculations further reveal
that the intrinsic piezoelectric response of these two low-symmetry triclinic
phases is not significantly large, which thus implies that the ease of phase
transition between these two energetically close triclinic phases is likely
responsible for the large piezoelectric response found in the BiFeO3 films near
its MPB. These findings not only enrich the understandings of the lattice and
domain structure of epitaxial BiFeO3 films but may also shed some light on the
origin of enhanced piezoelectric response near MPB.Comment: 19 pages, 3 figures and 1 tabl
The Effects of Ultra-high Pressure Treatment on the Phenolic Composition of Red Wine
Wine is usually aged in oak barrels. In this study, young red wines were treated with ultra-high pressure(UHP) to stimulate the ageing process. Changes in phenolic acids, flavan-3-ols and proanthocyanidinswere determined by reverse-phase high pressure liquid chromatography (RP-HPLC). The concentrationof phenolic acids increased, while the levels of flavan-3-ols decreased. The content and structure ofproanthocyanidins also changed and the tendency was similar to that of natural ageing
Human-Centered Design to Address Biases in Artificial Intelligence
The potential of artificial intelligence (AI) to reduce health care disparities and inequities is recognized, but it can also exacerbate these issues if not implemented in an equitable manner. This perspective identifies potential biases in each stage of the AI life cycle, including data collection, annotation, machine learning model development, evaluation, deployment, operationalization, monitoring, and feedback integration. To mitigate these biases, we suggest involving a diverse group of stakeholders, using human-centered AI principles. Human-centered AI can help ensure that AI systems are designed and used in a way that benefits patients and society, which can reduce health disparities and inequities. By recognizing and addressing biases at each stage of the AI life cycle, AI can achieve its potential in health care
- …