1,788 research outputs found
Layer Antiferromagnetic State in Bilayer Graphene : A First-Principle Investigation
The ground state of bilayer graphene is investigated by the density
functional calculations with local spin density approximation. We find a ground
state with layer antiferromagnetic ordering, which has been suggested by former
studies based on simplified model. The calculations prove that the layer
antiferromagnetic state (LAF) is stable even if the remote hopping and nonlocal
Coulomb interaction are included. The gap of the LAF state is about 1.8 meV,
comparable to the experimental value. The surface magnetism in BLG is of the
order of
Topological phase transition and nontrivial thermal Hall signatures in honeycomb lattice magnets
We investigate spinon band topology and engineering from the interplay
between long-ranged magnetic order and fractionalized spinons, as well as
Zeeman coupling under external magnetic fields, in honeycomb lattice magnets.
The synergism of N\'eel order and magnetic fields could reconstruct the spinon
bands and drive a topological phase transition from the coexisting phase of
long-ranged order and chiral spin liquid with semion topological order to the
conventional magnetic order. Our prediction can be immediately tested through
thermal Hall transport measurements among the honeycomb lattice magnets that
are tuned to be proximate to the quantum critical point. Our theory should also
shed light on the critical behavior of honeycomb Kitaev materials with emergent
Majorana fermion bands. We suggest a possible relevance to the spin-1/2
honeycomb spin liquid candidate material InCuVO.Comment: 6 figures, may submit to a domestic journal of China, paper
explanation is found
https://gangchengroup-physics.weebly.com/paper-explanation.htm
Carbon monoxide in an extremely metal-poor galaxy
Extremely metal-poor galaxies with metallicity below 10% of the solar value
in the local universe are the best analogues to investigating the interstellar
medium at a quasi-primitive environment in the early universe. In spite of the
ongoing formation of stars in these galaxies, the presence of molecular gas
(which is known to provide the material reservoir for star formation in
galaxies, such as our Milky Way) remains unclear. Here, we report the detection
of carbon monoxide (CO), the primary tracer of molecular gas, in a galaxy with
7% solar metallicity, with additional detections in two galaxies at higher
metallicities. Such detections offer direct evidence for the existence of
molecular gas in these galaxies that contain few metals. Using archived
infrared data, it is shown that the molecular gas mass per CO luminosity at
extremely low metallicity is approximately one-thousand times the Milky Way
value.Comment: 12 pages, 3 figures, 1 table. Supplementary data at
http://www.nature.com/article-assets/npg/ncomms/2016/161209/ncomms13789/extref/ncomms13789-s1.pd
Multi-Agent Game Abstraction via Graph Attention Neural Network
In large-scale multi-agent systems, the large number of agents and complex
game relationship cause great difficulty for policy learning. Therefore,
simplifying the learning process is an important research issue. In many
multi-agent systems, the interactions between agents often happen locally,
which means that agents neither need to coordinate with all other agents nor
need to coordinate with others all the time. Traditional methods attempt to use
pre-defined rules to capture the interaction relationship between agents.
However, the methods cannot be directly used in a large-scale environment due
to the difficulty of transforming the complex interactions between agents into
rules. In this paper, we model the relationship between agents by a complete
graph and propose a novel game abstraction mechanism based on two-stage
attention network (G2ANet), which can indicate whether there is an interaction
between two agents and the importance of the interaction. We integrate this
detection mechanism into graph neural network-based multi-agent reinforcement
learning for conducting game abstraction and propose two novel learning
algorithms GA-Comm and GA-AC. We conduct experiments in Traffic Junction and
Predator-Prey. The results indicate that the proposed methods can simplify the
learning process and meanwhile get better asymptotic performance compared with
state-of-the-art algorithms.Comment: Accepted by AAAI202
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