1,242 research outputs found
Higher-order Topology of Axion Insulator EuInAs
Based on first-principles calculations and symmetry analysis, we propose that
EuInAs is a long awaited axion insulator with antiferromagnetic (AFM)
long range order. Characterized by the parity-based invariant ,
the topological magneto-electric effect is quantized with in the
bulk, with a band gap as large as 0.1 eV. When the staggered magnetic moment of
the AFM phase is along axis, it's also a TCI phase. Gapless surface
states emerge on (100), (010) and (001) surfaces, protected by mirror
symmetries (nonzero mirror Chern numbers). When the magnetic moment is along
axis, the (100) and (001) surfaces are gapped. As a consequence of a
high-order topological insulator with , the one-dimensional (1D)
chiral state can exist on the hinge between those gapped surfaces. We have
calculated both the topological surface states and hinge state in different
phases of the system, respectively, which can be detected by ARPES or STM
experiments
Electric dipole sheets in BaTiO/BaZrO superlattices
We investigate two-dimensional electric dipole sheets in the superlattice
made of BaTiO and BaZrO using first-principles-based Monte-Carlo
simulations and density functional calculations. Electric dipole domains and
complex patterns are observed and the complex dipole structures with various
symmetries (e.g. Pma2, Cmcm and Pmc2_{1}) are further confirmed by density
functional calculations, which are found to be almost degenerate in energy with
the ferroelectric ground state of the Amm2 symmetry, therefore strongly
resembling magnetic sheets. More complex dipole patterns, including vortices
and anti-vortices, are also observed, which may constitute the intermediate
states that overcome the high energy barrier of different polarization
orientations previously predicted by Lebedev\onlinecite{Lebedev2013}. We also
show that such system possesses large electrostrictive effects that may be
technologically important
Magnetic field induced enhancement of spin-order peak intensity in La(1.875)Ba(0.125)CuO(4)
We report on neutron-scattering results on the impact of a magnetic field on
stripe order in the cuprate LaBaCuO. It is found that a
7 T magnetic field applied along the {\it c} axis causes a small but finite
enhancement of the spin-order peak intensity and has no observable effect on
the peak width. Inelastic neutron-scattering measurements indicate that the
low-energy magnetic excitations are not affected by the field, within
experimental error. In particular, the small energy gap that was recently
reported is still present at low temperature in the applied field. In addition,
we find that the spin-correlation length along the antiferromagnetic stripes is
greater than that perpendicular to them.Comment: 4 pages, 5 figure
A novel measurement method of toe debris thickness for bored piles based on one-dimensional wave theory
The existence of toe debris at the bottom of the bored pile will reduce the bearing capacity of the pile. This paper develops a novel equipment to measure the thickness of toe debris for bored piles. The equipment consists of a test rod, test hammer, velocimeter, transmission cable and data receiving and processing device. Based on the one-dimensional wave theory, the mechanism of the sudden change of the velocity time curve received at the top of the test rod is analyzed, which is caused by the change of the wave impedance at the interface between the test rod and the sediment, thus the feasibility of the equipment is verified in theory. Finally, numerical simulations of toe debris under various working conditions are carried out to verify the reliability of the equipment. The results show that the test curves are sensitive to the materials of test rod using proposed equipment when the thickness of toe debris is equal or greater than 50Â cm, and the test values are all larger than actual values, which meet the requirement of relevant specifications. The test results are more accuracy when the thickness of toe debris is less than 50Â cm. when the excited force is large, not only the sudden change is easy to be discriminated, but also the test accuracy can be assured. The remainder toe debris meet the requirement of relevant specifications after clearing pile hole according the proposed method. And the device is not affected by the properties of the sediment material, which indicates that the proposed equipment can perform well to test the thickness of toe debris
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