“Topological Quantum Matter Initiative” aims at accelerating the recent development in novel concept of quantum mechanics and realizing its engineering application by noting emerging researches in topological materials group and diverse material properties associated with topology. Typical examples of its application are quantum computing, spintronics, photonics, in which device innovation occurs by introduction of the novel topological concepts to go beyond the present technological framework and contributes to the “super smart society”. Requirements for downsizing, higher speed and lower energy consumption in electronic devices becomes stronger world-wide in recent years, and innovative technical paradigm is strongly desired since limitations become apparent in existing device technologies, as is seen in the end of Moore’s Law for semiconductor devises.
In order to overcome these limitations, we propose an R&D strategy, which leads to innovation utilizing novel phenomena and functions inherent to topological materials. Three major directions to overcome the limitations in CMOS technology are proposed as follows: One is three-dimensional heterogeneous integration of devices with diverse functions, the second is introduction of novel architecture, such as neuromorphic computing or quantum computing, and the third is device innovation by introducing new materials, such as graphene or topological materials. In this proposal we focus on the second and third trends. In particular, we aim at causing innovation in diverse R&D fields such as quantum computing, non-volatile logics, and optical integrated circuits for communication, starting from topological materials and unique physical properties associated with topology.
Topology is the mathematical concept of the properties that are preserved through deformation, twisting, and stretching of objects. By applying the concept of topology to the material system, “topological material” is introduced as a novel type of the material phase, which cannot be described in terms of the conventional category of metal, semiconductor, or insulator. A topological insulator, a typical example of topological material, is a material with non-trivial topological order that behaves as an insulator in its interior but whose surface contains conducting states, which is caused by unique electronic structure at the surface. By reclassifying materials using the topological concepts, a new material viewpoint different from conventional one has gradually arisen. This means topological concepts provide possibilities that new phenomena and new functions are discovered not only in new materials but also in known ones, and that candidate material group leading to practical applications is expected to expand.
Based on considerations described above, this proposal aims at both technical development of engineering application using topological properties in the materials and strengthening of related academic basis. Subjects of R&D to achieve these aims consist of three categories, which are “construction of theoretical framework”, “creation of new topological materials and establishment of technologies to control unique properties appearing in those materials”, and “development of technology for device application”.
Theoretical prediction of topological materials and their unique physical phenomenon has preceded mostly their experimental discoveries. In order to promote engineering application of those materials, establishment of a theoretical framework and a firm stage of device technology where topological materials play a key role is required. In addition, it is strongly required to develop technologies for creation of novel materials, control of their functions, and characterization of their properties. It is also desired that possibilities should be sought for application of topological materials in the unexploited fields such as phononics, mechanics and chemical reactions, in addition to typical applications such as quantum computing, spintronics and photonics.
In order to conduct R&D for topological quantum initiative, it is strongly expected to establish an interdisciplinary research involving solid state physics, elementary particle physics and mathematics, as well as collaborations with electronics and measurement engineers to realize novel devices based on the topological materials. Therefore, it is expected to change gear to promote researches from the basic stage to higher ones. For this purpose, collaborative works between scientific and engineering researchers are important. Construction of framework of political inducement is needed to purposely direct curiosity-driven researches at academia to engineering application. Long-range viewpoint is also important to cultivate human resources who bear R&D in Japan by establishing suitable environment for young researchers to challenge the risky novel multidisciplinary field.
It should be noted that the Station Q of Microsoft Research gathers professionals of mathematics, computational science and quantum physics together to develop the quantum computing technology utilizing topological phenomena. In contrast, Japanese industries are far behind the approach to quantum computing. Therefore, it is necessary for the research community engaged in R&D of topological materials to announce the importance of this field to industry people and actively promote R&D projects by involving industry people. For this purpose, “future vision concept creating meeting (tentative name)” which consists of opinion leaders, young researchers and industry is necessary to be held regularly with the objectives of sharing the information, discussing the future direction of R&D, and matching of seeds and needs. Furthermore, it is also quite important to establish strategic collaborations and human exchanges with research organizations in overseas.