Topological Properties and Functionalities in Oxide Thin Films and Interfaces

As symbolized by the Nobel Prize in Physics 2016, "topology" has been recognized as an essential standpoint to understand and control the physics of condensed matter. This concept may be spreading even into application areas such as novel electronics. In this trend, there has been reported a number of study for the oxide films and heterostructures with topologically non-trivial electronic or magnetic states. In this review, we overview the trends of new topological properties and functionalities in oxide materials with sorting out a number of examples. The technological advances in oxide film growth achieved over the last few decades are now opening the door for harnessing novel topological properties.Comment: 15 pages, 7 figure

Analysis of the Image for Landscape of Port City

The purpose of this study is to obtain basic information available to make a new design concept at the first stage of landscape planning. Recently, with the large change of waterfront spaces, urban environments around port cities are getting more serious in Japan. So it is nesessary to begin planning to recreate the landscapes and facilities. However in this case we should consider the people's image and impression on curtural climate or environments to make fascinating townscapes. We sconsider two positions of people's image denned. One is the Media Image, and the other is the Residents' Image. Many current topics on tourist resorts or fascinating landscapes have been usually reported by visual and linguistic mass media in Japan. Many people form their images on townscapes without real experience. This image is called the Media Image and represents the external people's hope for spaces. On the other hand, the internal residents in the port city form their image by real experience or influence on their lives. This image is defined as the Residents' Image. Through a psychological experiment under the stimulus of visual media, this study specifies basic characteristics of the visual landscapes at representative port cities in Japan by comparing the two images

Andreev reflection at the interface with an oxide in the quantum Hall regime

Quantum Hall/superconductor junctions have been an attractive topic as the two macroscopically quantum states join at the interface. Despite longstanding efforts, however, experimental understanding of this system has not been settled yet. One of the reasons is that most semiconductors hosting high-mobility two-dimensional electron systems (2DES) usually form Schottky barriers at the metal contacts, preventing efficient proximity between the quantum Hall edge states and Cooper pairs. Only recently have relatively transparent 2DES/superconductor junctions been investigated in graphene. In this study, we propose another material system for investigating 2DES/superconductor junctions, that is ZnO-based heterostrcuture. Due to the ionic nature of ZnO, a Schottky barrier is not effectively formed at the contact with a superconductor MoGe, as evidenced by the appearance of Andreev reflection at low temperatures. With applying magnetic field, while clear quantum Hall effect is observed for ZnO 2DES, conductance across the junction oscillates with the filling factor of the quantum Hall states. We find that Andreev reflection is suppressed in the well developed quantum Hall regimes, which we interpret as a result of equal probabilities of normal and Andreev reflections as a result of multiple Andreev reflection at the 2DES/superconductor interface.Comment: 18 pages, 8 figure

Blue light-emitting diode based on ZnO

A near-band-edge bluish electroluminescence (EL) band centered at around 440 nm was observed from ZnO p-i-n homojunction diodes through a semi-transparent electrode deposited on the p-type ZnO top layer. The EL peak energy coincided with the photoluminescence peak energy of an equivalent p-type ZnO layer, indicating that the electron injection from the n-type layer to the p-type layer dominates the current, giving rise to the radiative recombination in the p-type layer. The imbalance in charge injection is considered to originate from the lower majority carrier concentration in the p-type layer, which is one or two orders of magnitude lower than that in the n-type one. The current-voltage characteristics showed the presence of series resistance of several hundreds ohms, corresponding to the current spread resistance within the bottom n-type ZnO. The employment of conducting ZnO substrates may solve the latter problem.Comment: 13 pages, 4 figures. Jpn. J. Appl. Phys. in pres