88 research outputs found
Excitations in the ordered and paramagnetic states of honeycomb magnet Na2Co2TeO6
Na2Co2TeO6 is a proposed approximate Kitaev magnet, yet its actual magnetic
interactions are elusive due to a lack of knowledge on the full excitation
spectrum. Here, using inelastic neutron scattering and single crystals, we
determine the system's temperature-dependent magnetic excitations over the
entire Brillouin zone. Without committing to specific models, we unveil a
distinct signature of the third-nearest-neighbor coupling in the spin waves,
which signifies the associated distance as an emerging "soft link" in the
ordered state. The presence of at least six non-overlapping spin-wave branches
is at odds with all models proposed to date. Above the ordering temperature,
persisting dynamic correlations can be described by equal-time magnetic
structure factors of a hexagonal cluster, which reveal the leading
instabilities. Our result sets definitive constraint on theoretical models for
Na2Co2TeO6 and provides new insight for the materialization of the Kitaev
model.Comment: 4 pages, 4 figures plus Supplemental Material; comments are welcom
Implementation of Respecting and Safeguarding Human Rights Provisions at the Criminal Justice
The amended “Code of Criminal Procedure” in 2012 has written “respecting and safeguarding human rights” into the Article 2 of this provision. This is a tremendous progress in our criminal justice. Essentially, the fundamental purpose of criminal justice system is to safeguard citizens, especially the human rights of criminal suspects and criminal defendants. Currently, although the criminal justice system in China has made significantly progress in the protection of human rights in recent years, there are still many problems. By the occasion of the amendment to the “Code of Criminal Procedure”, it should further improve human rights protection mechanisms of criminal justice in China and raise the legalization level of criminal justice in China.Key words: Human rights protection; Criminal justice; Code of criminal procedur
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Phononic-magnetic dichotomy of the thermal Hall effect in the Kitaev material Na2 Co2 TeO6
The quest for a half-quantized thermal Hall effect of a Kitaev system represents an important tool to probe topological edge currents of emergent Majorana fermions. Pertinent experimental findings for α-RuCl3 are, however, strongly debated, and it has been argued that the thermal Hall signal stems from phonons or magnons rather than from Majorana fermions. Here, we investigate the thermal Hall effect of the Kitaev candidate material Na2Co2TeO6, and we show that the measured signal emerges from at least two components, phonons and magnetic excitations. This dichotomy results from our discovery that the longitudinal and transversal heat conductivities share clear phononic signatures, while the transversal signal changes sign upon entering the low-temperature, magnetically ordered phase. Our results demonstrate that uncovering a genuinely quantized magnetic thermal Hall effect in Kitaev topological quantum spin liquids such as α-RuCl3 and Na2Co2TeO6 requires disentangling phonon vs magnetic contributions, including potentially fractionalized excitations such as the expected Majorana fermions
Magnetic ground state of the Kitaev NaCoTeO spin liquid candidate
As a candidate Kitaev material, NaCoTeO exhibits intriguing
magnetism on a honeycomb lattice that is believed to be -symmetric. Here
we report a neutron diffraction study of high quality single crystals under
-axis magnetic fields. Our data support the less common notion of a magnetic
ground state that corresponds to a triple- magnetic structure with
symmetry, rather than the multi-domain zigzag structure typically assumed
in prototype Kitaev spin liquid candidates. In particular, we find that the
field is unable to repopulate the supposed zigzag domains, where the only
alternative explanation is that the domains are strongly pinned by hitherto
unidentified structural reasons. If the triple- structure is
correct then this requires reevaluation of many candidate Kitaev materials. We
also find that fields beyond about 10 Tesla suppress the long range
antiferromagnetic order, allowing new magnetic behavior to emerge different
from that expected for a spin liquid.Comment: 4 pages, 4 figures, plus Supplemental Materia
Near infrared spectroscopy coupled with radial basis function neural network for at-line monitoring of Lactococcus lactis subsp. fermentation
AbstractIn our previous work, partial least squares (PLSs) were employed to develop the near infrared spectroscopy (NIRs) models for at-line (fast off-line) monitoring key parameters of Lactococcus lactis subsp. fermentation. In this study, radial basis function neural network (RBFNN) as a non-linear modeling method was investigated to develop NIRs models instead of PLS. A method named moving window radial basis function neural network (MWRBFNN) was applied to select the characteristic wavelength variables by using the degree approximation (Da) as criterion. Next, the RBFNN models with selected wavelength variables were optimized by selecting a suitable constant spread. Finally, the effective spectra pretreatment methods were selected by comparing the robustness of the optimum RBFNN models developed with pretreated spectra. The results demonstrated that the robustness of the optimal RBFNN models were better than the PLS models for at-line monitoring of glucose and pH of L. lactis subsp. fermentation
Tuning the Magnetism in Ultrathin CrxTey Films by Lattice Dimensionality
Two-dimensional (2D) magnetic transition metal compounds with atomic
thickness exhibit intriguing physics in fundamental research and great
potential for device applications. Understanding the correlations between their
macrosopic magnetic properties and the dimensionality of microscopic magnetic
exchange interactions are valuable for the designing and applications of 2D
magnetic crystals. Here, using spin-polarized scanning tunneling microscopy,
magnetization and magneto-transport measurements, we identify the
zigzag-antiferromagnetism in monolayer CrTe2, incipient ferromagnetism in
bilayer CrTe2, and robust ferromagnetism in bilayer Cr3Te4 films. Our density
functional theory calculations unravel that the magnetic ordering in ultrathin
CrTe2 is sensitive to the lattice parameters, while robust ferromagnetism with
large perpendicular magnetic anisotropy in Cr3Te4 is stabilized through its
anisotropic 3D magnetic exchange interactions
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