99,951 research outputs found
3d Transition Metal Adsorption Induced Vally-polarized Anomalous Hall Effect in Germanene
Based on DFT+U and Berry curvature calculations, we study the electronic
structures and topological properties of 3d transition metal (TM) atom (from Ti
to Co) adsorbed germanene (TM-germanene). We find that valley-polarized
anomalous hall effect (VAHE) can be realized in germanene by adsorbing Cr, Mn,
or Co atom on its surface. A finite valley hall voltage can be easily detected
in its nanoribbon, which is important for valleytronics devices. Moreover,
different valley-polarized current and even reversible valley Hall voltage can
be archived by shifting the Fermi energy of the systems. Such versatile
features of the systems show potential in next generation electronics devices.Comment: 8 pages, 7 figure
Two Dimensional Antiferromagnetic Chern Insulator NiRuCl6
Based on DFT and Berry curvature calculations, we predict that quantum
anomalous hall effect (QAHE) can be realized in two dimensional
anti-ferromagnetic (AFM) NiRuCl6 with zero net magnetic moment. By tuning
spin-orbits coupling (SOC), we find that the topological properties of NiRuCl6
come from its energy band reversal. The results indicate that NiRuCl6 behaves
as AFM Chern insulator and its spin-polarized electronic structure and strong
spin-orbits coupling (SOC) are the origin of QAHE. Considering the
compatibility between AFM and insulator, AFM Chern insulator is more suitable
to realize high temperature QAHE because generally Neel temperature of AFM
systems is more easily improved than Curie temperature of ferromagnetic (FM)
systems. Due to the different magnetic coupling mechanism between FM and AFM
Chern insulator, AFM Chern insulator provides a new way to archive high
temperature QAHE in experiments.Comment: 6 pages, 6 figure
Second order quantum decoherence in the boson system
The second order quantum decoherence (SOQDC)is proposed as a novel
description for the loss of quantum coherence only reflected by second order
quantum correlations. By calculating the two-time correlation function, the
phenomenon of SOQDC is studied in details for a simple model, a two boson
system interacting with a reservoir composed of one or many bosons. The second
order quantum decoherence effects can be observed in the sketched cavity QED
experiment.Comment: 4 pages, 3 figures, revtex, corrected some typo
PILAE: A Non-gradient Descent Learning Scheme for Deep Feedforward Neural Networks
In this work, a non-gradient descent learning scheme is proposed for deep
feedforward neural networks (DNN). As we known, autoencoder can be used as the
building blocks of the multi-layer perceptron (MLP) deep neural network. So,
the MLP will be taken as an example to illustrate the proposed scheme of
pseudoinverse learning algorithm for autoencoder (PILAE) training. The PILAE
with low rank approximation is a non-gradient based learning algorithm, and the
encoder weight matrix is set to be the low rank approximation of the
pseudoinverse of the input matrix, while the decoder weight matrix is
calculated by the pseudoinverse learning algorithm. It is worth to note that
only few network structure hyperparameters need to be tuned. Hence, the
proposed algorithm can be regarded as a quasi-automated training algorithm
which can be utilized in autonomous machine learning research field. The
experimental results show that the proposed learning scheme for DNN can achieve
better performance on considering the tradeoff between training efficiency and
classification accuracy.Comment: This work is our effort toward to realize AutoM
Open Type Nodal line Topological Semimetal in Two Dimensional B2C
Topological semimetals, including Dirac semimetals, Weyl semimetals, and
nodal line semimetals, receive enormous research interest due to their
intrinsic topological nature and fascinating properties. In present work, with
the help of density functional theory (DFT), we find that nodal line semimetals
and Dirac semimetals can coexist in the low energy electron of two dimensional
(2D) monolayer B2C. Intriguingly, besides type-I and type-II Dirac fermions, a
kind of open nodal line appears around the Fermi level. The low energy
electronic nature of B2C sheet can be described by a tight-binding (TB) model
relied on the basis of B-py, pz and C-py, pz states. One of the most merit of
the system is that the energy windows of these four types topological
semimetals are different that can be easily distinguished in experiments.
Moreover, the system provides an excellent platform for studying the interplay
between different type semimetals.Comment: 9 pages, 6 figure
A criterion for testing multi-particle NPT entanglement
We revisit the criterion of multi-particle entanglement based on the overlaps
of a given quantum state with maximally entangled states. For a system
of particles, each with distinct states, we prove that is
-particle negative partial transpose (NPT) entangled, if there exists a
maximally entangled state , such that . While this sufficiency condition is weaker than the
Peres-Horodecki criterion in all cases, it applies to multi-particle systems,
and becomes especially useful when the number of particles () is large. We
also consider the converse of this criterion and illustrate its invalidity with
counter examples.Comment: 4 page
Magnetic structure and domain conversion of quasi-2D frustrated antiferromagnet CuCrO2 probed by NMR
We have carried out 63,65Cu NMR spectra measurements in magnetic field up to
about 15.5 T on single crystal of a multiferroic triangular-lattice
antiferromagnet CuCrO2. The measurements were performed for perpendicular and
parallel orientation of the magnetic field with respect to the c-axis of the
crystal, and the detailed angle dependence of the spectra on the magnetic field
direction within ab-plane was studied. The shape of the spectra can be well
described in the model of spiral spin structure proposed by recent neutron
diffraction experiments. When field is rotated perpendicular to crystal c-axis,
we observed, directly for the first time, a remarkable reorientation of spin
plane simultaneous with rotation of the incommensurate wavevector by
quantitatively deducing the conversion of less energetically favorable domain
to a more favorable one. At high enough fields parallel to c-axis, the data are
consistent with either a field-induced commensurate spiral magnetic structure
or an incommensurate spiral magnetic structure with a disorder in the c
direction, suggesting that high fields may have influence on interplanar
ordering.Comment: 8 pages, 10 figure
Magnetic phases of quasi-two-dimensional antiferromagnet on triangular lattice CuCrO
We have carried out Cu NMR spectra measurements in magnetic field
up to about 45~T on single crystal of a multiferroic triangular antiferromagnet
CuCrO. The measurements were performed for magnetic fields aligned along
the crystal -axis. Field and temperature evolution of the spectral shape
demonstrates a number of phase transitions. It was found that the 3D magnetic
ordering takes place in the low field range (~T). At higher fields
magnetic structures form within individual triangular planes whereas the spin
directions of the magnetic ions from neighboring planes are not correlated. It
is established that the 2D-3D transition is hysteretic in field and
temperature. Lineshape analysis reveals several possible magnetic structures
existing within individual planes for different phases of CuCrO. Within
certain regions on the magnetic H-T phase diagram of CuCrO a 3D magnetic
ordering with tensor order parameter is expected
Second Quantization of Cini Model for High Order Quantum Decoherence in Quantum Measurement
By making the second quantization for the Cini Model of quantum measurement
without wave function collapse [M. Cini, Nuovo Cimento, B73 27(1983)], the
second order quantum decoherence (SOQD) is studied with a two mode boson system
interacting with an idealized apparatus composed by two quantum oscillators. In
the classical limit that the apparatus is prepared in a Fock state with a very
large quantum number, or in a coherent state with average quantum numbers large
enough, the SOQD phenomenon appears similar to the first order case of quantum
decoherence.Comment: 12 pages, revtex, 2 figure
Quantum teleportation using cluster states
A protocol of quantum communication is proposed in terms of the multi-qubit
quantum teleportation through cluster states (Phys. Rev. Lett. \textbf{86}, 910
(2001)). Extending the cluster state based quantum teleportation on the basic
unit of three qubits (or qudits), the corresponding multi-qubit network is
constructed for both the qubits and qudits (multi-level) cases. The classical
information costs to complete this communication task is also analyzed. It is
also shown that this quantum communication protocol can be implemented in the
spin-spin system on lattices.Comment: 4 pages, 2 figure
- …