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Akira Tonomura

Publications and source records attributed to Akira Tonomura.

7 recordsLinked to original sources
PubMed2005

Direct observation of thitherto unobservable quantum phenomena by using electrons.

Fundamental aspects of quantum mechanics, which were discussed only theoretically as "thought experiments" in the 1920s and 1930s, have begun to frequently show up in nanoscopic regions owing to recent rapid progress in advanced technologies. Quantum phenomena were once regarded as the ultimate factors limiting further miniaturization trends of microstructured electronic devices, but now they have begun to be actively used as the principles for new devices such as quantum computers. To directly observe what had been unobservable quantum phenomena, we have tried to develop bright and monochromatic electron beams for the last 35 years. Every time the brightness of an electron beam improved, fundamental experiments in quantum mechanics became possible, and quantum phenomena became observable by using the wave nature of electrons.

Biophysical Phenomena↗
PubMed2005

Direct observation of rectified motion of vortices in a niobium superconductor.

Using Lorentz microscopy to directly image vortices, we investigate vortex motion control and rectification in a niobium superconductor. We directly observe a net motion of vortices along microfabricated channels with a spatially asymmetric potential, even though the vortices were driven by an oscillatory field. By observing the individual motion of vortices, we clarify elementary processes involved in this rectification. To further demonstrate the ability to control the motion of vortices, we created a tiny vortex "racetrack" to monitor the motion of vortices in a closed circuit channel.

Journal Article↗
PubMed2005

Optical system for double-biprism electron holography.

A novel system of electron interferometry and holography using two electron biprisms has been developed. The first biprism is installed in the image plane of the objective lens and the second one is set behind the first magnifying lens, inside the shadow area of the first biprism. The system can independently control two important parameters for interferograms and holograms, the fringe spacing and interference width. Thus, it gives us more flexibility on performing electron interferometry and holography. The good performance of the system was demonstrated using a 1MV field-emission electron microscope. We introduce a variety of optical set-ups for the system and explain the advantages of each set-up in detail, with experimental results.

Journal Article↗
PubMed2003

Applications of 1 MV field-emission transmission electron microscope.

A newly developed 1 MV field-emission transmission electron microscope has recently been applied to the field of superconductivity by utilizing its bright and monochromatic field-emission electron beam. This microscope allows individual magnetic vortices inside high-Tc superconductors to be observed, thus, opening the way to investigate the unusual behaviour of vortices, which reflects the anisotropic layered structure of these superconducting materials. One example is the observation of the arrangements of chain vortex lines that are formed when a magnetic field is applied obliquely to the layer plane of the materials.

Journal Article↗
PubMed2003

Profile structure of magnetic flux lines in type-II superconductor from a rectangular electron hologram.

Profile magnetic configuration of a quantized flux line and flux-line lattice penetrating a type-II superconductor thin foil, niobium, was observed by electron holography and Lorentz microscopy using a 300 kV field-emission electron microscope. Each single flux line was distributed periodically as lattice structure in the mixed state just below its critical temperature of 8.5 K, while at low temperature of 5 K the flux lines were weakly bound as bundles. In order to observe the flux-line distribution over a wide area, discrete Fourier transform reconstruction in the holography was extended for a rectangular area without loss of information and data precision.

Journal Article↗