2,606 research outputs found
Half Metallic Bilayer Graphene
Charge neutral bilayer graphene has a gapped ground state as transport
experiments demonstrate. One of the plausible such ground states is layered
antiferromagnetic spin density wave (LAF) state, where the spins in top and
bottom layers have same magnitude with opposite directions. We propose that
lightly charged bilayer graphene in an electric field perpendicular to the
graphene plane may be a half metal as a consequence of the inversion and
particle-hole symmetry broken in the LAF state. We show this explicitly by
using a mean field theory on a 2-layer Hubbard model for the bilayer graphene.Comment: 4+ pages, 4 figure
Majorana corner modes and flat-band Majorana edge modes in superconductor/topological-insulator/superconductor junctions
Recently, superconductors with higher-order topology have stimulated
extensive attention and research interest. Higher-order topological
superconductors exhibit unconventional bulk-boundary correspondence, thus allow
exotic lower-dimensional boundary modes, such as Majorana corner and hinge
modes. However, higher-order topological superconductivity has yet to be found
in naturally occurring materials. In this work, we investigate higher-order
topology in a two-dimensional Josephson junction comprised of two -wave
superconductors separated by a topological insulator thin film. We found that
zero-energy Majorana corner modes, a boundary fingerprint of higher-order
topological superconductivity, can be achieved by applying magnetic field. When
an in-plane Zeeman field is applied to the system, two corner states appear in
the superconducting junction. Furthermore, we also discover a two dimensional
nodal superconducting phase which supports flat-band Majorana edge modes
connecting the bulk nodes. Importantly, we demonstrate that zero-energy
Majorana corner modes are stable when increasing the thickness of topological
insulator thin film.Comment: 9 pages, 4 figure
Mathematical Model and Analysis of the Water-Lubricated Hydrostatic Journal Bearings considering the Translational and Tilting Motions
The water-lubricated bearings have been paid attention for their advantages to reduce the power loss and temperature rise and increase load capacity at high speed. To fully study the complete dynamic coefficients of two water-lubricated, hydrostatic journal bearings used to support a rigid rotor, a four-degree-of-freedom model considering the translational and tilting motion is presented. The effects of tilting ratio, rotary speed, and eccentricity ratio on the static and dynamic performances of the bearings are investigated. The bulk turbulent Reynolds equation is adopted. The finite difference method and a linear perturbation method are used to calculate the zeroth- and first-order pressure fields to obtain the static and dynamic coefficients. The results suggest that when the tilting ratio is smaller than 0.4 or the eccentricity ratio is smaller than 0.1, the static and dynamic characteristics are relatively insensitive to the tilting and eccentricity ratios; however, for larger tilting or eccentricity ratios, the tilting and eccentric effects should be fully considered. Meanwhile, the rotary speed significantly affects the performance of the hydrostatic, water-lubricated bearings
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