1,704 research outputs found
Landau level states on a topological insulator thin film
We analyze the four-dimensional Hamiltonian proposed to describe the band
structure of the single-Dirac-cone family of topological insulators in the
presence of a uniform perpendicular magnetic field. Surface Landau level(LL)
states appear, decoupled from the bulk levels and following the quantized
energy dispersion of a purely two-dimensional surface Dirac Hamiltonian. A
small hybridization gap splits the degeneracy of the central n=0 LL with
dependence on the film thickness and the field strength that can be obtained
analytically. Explicit calculation of the spin and charge densities show that
surface LL states are localized within approximately one quintuple layer from
the surface termination. Some new surface-bound LLs are shown to exist at a
higher Landau level index.Comment: 8 pages, 4 figure
Multiple nodal solutions of nonlinear Choquard equations
In this paper, we consider the existence of multiple nodal solutions of the
nonlinear Choquard equation \begin{equation*} \ \ \ \ (P)\ \ \ \ \begin{cases}
-\Delta u+u=(|x|^{-1}\ast|u|^p)|u|^{p-2}u \ \ \ \text{in}\ \mathbb{R}^3, \ \ \
\ \\ u\in H^1(\mathbb{R}^3),\\ \end{cases} \end{equation*} where . We show that for any positive integer , problem has
at least a radially symmetrical solution changing sign exactly -times
Enhancement of Visible-Light-Induced Photocurrent and Photocatalytic Activity of V and N Codoped TiO2 Nanotube Array Films
Highly ordered TiO2 nanotube arrays (TNAs) codoped with V and N were
synthesized by electrochemical anodization in association with hydrothermal
treatment. The samples were characterized by field emission scanning electron
microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The
photocurrent and photocatalytic activity of codoped TiO2 nanotube arrays were
investigated under visible light irradiation. Moreover, the production of
hydroxyl radicals on the surface of visible light-irradiated samples is
detected by a photoluminescence technique using terephthalic acid (TA) as a
probe molecule. It was found that the V+N co-doped TiO2 nanotube arrays showed
remarkably enhanced photocurrent and photocatalytic activity than undoped
sample due to the V and N codoping.Comment: 15 Pages, 6 figure
3D-PhysNet: Learning the Intuitive Physics of Non-Rigid Object Deformations
The ability to interact and understand the environment is a fundamental
prerequisite for a wide range of applications from robotics to augmented
reality. In particular, predicting how deformable objects will react to applied
forces in real time is a significant challenge. This is further confounded by
the fact that shape information about encountered objects in the real world is
often impaired by occlusions, noise and missing regions e.g. a robot
manipulating an object will only be able to observe a partial view of the
entire solid. In this work we present a framework, 3D-PhysNet, which is able to
predict how a three-dimensional solid will deform under an applied force using
intuitive physics modelling. In particular, we propose a new method to encode
the physical properties of the material and the applied force, enabling
generalisation over materials. The key is to combine deep variational
autoencoders with adversarial training, conditioned on the applied force and
the material properties. We further propose a cascaded architecture that takes
a single 2.5D depth view of the object and predicts its deformation. Training
data is provided by a physics simulator. The network is fast enough to be used
in real-time applications from partial views. Experimental results show the
viability and the generalisation properties of the proposed architecture.Comment: in IJCAI 201
A novel method for computing the Hilbert transform with Haar multiresolution approximation
AbstractIn this paper, an algorithm for computing the Hilbert transform based on the Haar multiresolution approximation is proposed and the L2-error is estimated. Experimental results show that it outperforms the library function ‘hilbert’ in Matlab (The MathWorks, Inc. 1994–2007). Finally it is applied to compute the instantaneous phase of signals approximately and is compared with three existing methods
Metamagnetic transitions and anomalous magnetoresistance in EuAgAs single crystal
In this paper, the magnetic and transport properties were systematically
studied for EuAgAs single crystals, crystallizing in a centrosymmetric
trigonal CaCuP type structure. It was confirmed that two magnetic
transitions occur at = 10 K and = 15 K,
respectively. With the increasing field, the two transitions are noticeably
driven to lower temperature. At low temperatures, applying a magnetic field in
the plane induces two successive metamagnetic transitions. For
both and
, EuAgAs shows a positive, unexpected large
magnetoresistance (up to 202\%) at low fields below 10 K, and a large negative
magnetoresistance (up to -78\%) at high fields/intermediate temperatures. Such
anomalous field dependence of magnetoresistance may have potential application
in the future magnetic sensors. Finally, the magnetic phase diagrams of
EuAgAs were constructed for both
and
- …