We present the result of our most recent search for T-violation in 205 Tl, which is interpreted in terms of an electric dipole moment of the electron de. We find de = (6.9 ± 7.4) × 10 −28 e cm. The present apparatus is a major upgrade of the atomic beam magnetic-resonance device used to set the previous limit on de. PACS numbers: 11.30.Er, 14.60.Cd, 32.10.Dk We report a new result in the search for the electric dipole moment (EDM) of the electron, a quantity of interest in connection with CP violation and extensions to the standard model of particle physics [1][2][3]. In heavy paramagnetic atoms an electron EDM results in an atomic EDM enhanced by a factor R ≡ d atom /d e . Thus we search for a permanent EDM of atomic thallium in the 6 2 P 1/2 F = 1 ground state, where R −585 [4]. Experimental MethodLike its predecessor [5,6], the new experiment [7] uses magnetic resonance with two oscillating rf fields [8] separated by a space containing an intense electric field E, and employs laser optical pumping for state selection and analysis. To control systematic effects arising from motional magnetic fields E × v/c, the previous experiment employed a single pair of counterpropagating vertical atomic beams. The present experiment has two pairs separated by 2.54 cm, each consisting of Tl and Na (see Fig.1). The spatially separated beams are nominally exposed to identical magnetic but opposite electric fields; this provides common-mode noise rejection and control of some systematic effects. Sodium serves as a comagnetometer: it is susceptible to the same systematic effects but insensitive to d e , since R is roughly proportional to the cube of the nuclear charge. Furthermore, sodium's two 3 2 S 1/2 ground state hyperfine levels F =2, 1 have g F = ±1/2, which in principle permits the separation of two different types of motional field effects. Figure 1 shows a schematic diagram of the experiment with the up beams active. Atoms leave the trichamber oven thermally distributed among the ground state hyperfine levels. After some collimation they enter the quantizing magnetic field B, nominally in theẑ direction and typically 0.38 Gauss. Laser beams then depopulate the states with non-zero magnetic quantum numbers m F . Thus, in the first optical region 590 nm z polarized light selects the m F = 0 Zeeman sublevel of either the F = 2 or the F = 1 Na ground state. (B Tl cos ω Tl t + B Na cos ω Na t)x, where 2B Tl = B Na and 1.506ω Tl ω Na . These resonant fields apply 'π/2' pulses, creating coherent superpositions of the m F = 0 states of each species. The atoms then move into the electric field, nominally parallel or anti-parallel to B. Typically |E| = 1.23 × 10 5 V/cm. The second rf field is coherent with the first, differing only by a relative phase shift α. In the analysis regions the atoms are probed with the same laser that performed the state selection. Fluorescence photons accompanying the atomic decays are reflected by polished aluminum paraboloids into Winston cones [9] made of UV-transmitting plastic. These lightpi...

Resistive switching (RS) is an interesting property shown by some materials systems that, especially during the last decade, has gained a lot of interest for the fabrication of electronic devices, with electronic nonvolatile memories being those that have received the most attention. The presence and quality of the RS phenomenon in a materials system can be studied using different prototype cells, performing different experiments, displaying different figures of merit, and developing different computational analyses. Therefore, the real usefulness and impact of the findings presented in each study for the RS technology will be also different. This manuscript describes the most recommendable methodologies for the fabrication, characterization, and simulation of RS devices, as well as the proper methods to display the data obtained. The idea is to help the scientific community to evaluate the real usefulness and impact of an RS study for the development of RS technology.

Transmission electron microscopy is a powerful imaging tool that has found broad application in materials science, nanoscience and biology. With the introduction of aberration-corrected electron lenses, both the spatial resolution and the image quality in transmission electron microscopy have been significantly improved and resolution below 0.5 ångströms has been demonstrated. To reveal the three-dimensional (3D) structure of thin samples, electron tomography is the method of choice, with cubic-nanometre resolution currently achievable. Discrete tomography has recently been used to generate a 3D atomic reconstruction of a silver nanoparticle two to three nanometres in diameter, but this statistical method assumes prior knowledge of the particle's lattice structure and requires that the atoms fit rigidly on that lattice. Here we report the experimental demonstration of a general electron tomography method that achieves atomic-scale resolution without initial assumptions about the sample structure. By combining a novel projection alignment and tomographic reconstruction method with scanning transmission electron microscopy, we have determined the 3D structure of an approximately ten-nanometre gold nanoparticle at 2.4-ångström resolution. Although we cannot definitively locate all of the atoms inside the nanoparticle, individual atoms are observed in some regions of the particle and several grains are identified in three dimensions. The 3D surface morphology and internal lattice structure revealed are consistent with a distorted icosahedral multiply twinned particle. We anticipate that this general method can be applied not only to determine the 3D structure of nanomaterials at atomic-scale resolution, but also to improve the spatial resolution and image quality in other tomography fields.