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Integrated Function Engineering

We are studying physical phenomena on microfabricated superconducting and/or ferromagnetic materials. Our goal is to obtain "next generation devices," which overcomes the limit of present technology on semiconducting devices. In order to explore the potential functions of novel materials, our research covers from fundamental solid state physics to integrated device technologies such as growth of high-quality epitaxial thin-film and micro-fabrication.

Academic Staff

Itsuhiro KAKEYA

Itsuhiro KAKEYAAssociate Professor (Graduate School of Engineering)

Research Interests

  • Superconductivity, especially HTSC
  • Charge density wave
  • Magnetism
  • Other quantum conducting phenomena

Classes

  • Physics Lab
  • Electric Lab

Contacts

A1-307, A-Cluster, Katsura Campus
TEL: +81-75-383-2265
FAX: +81-75-383-2270
E-mail: kakeya_at_kuee.kyoto-u.ac.jp

Introduction to R&D Topics

Study on high-temperature superconductivity with inter-layer tunneling spectroscopy.

Some high-Tc superconductors (HTSC) have layered crystal structures, which contain alternatively stacked superconducting and insulating atomic layers. Since these stacks work as Josephson junctions originated from inherent crystal structures, these layered superconductors are called as "Intrinsic Josephson junctions (IJJ)." These integrated functional materials, where device functions are accumulated into naturally formed crystals, have large potentials for practical applications.

It is quite important to understand physics on HTSC in order to bring out these possibilities. Tunneling spectroscopy is one of powerful probes to reveal behaviors of electrons in the superconducting states. Since IJJs have naturally-formed perfect interfaces, which cannot be realized in artificially fabricated Josephson junctions, ideal tunnel-type Josephson junction properties can be obtained. Therefore, tunneling spectroscopy of IJJ may reveal genuine properties of HTSC.

We have found typical current-voltage (I-V) characteristics of Josephson (superconducting) current and quasiparticle (normal) current of HTSC from measurements on mesoscopic mesa structures of Bismuth HTSC compounds prepared by applying micro-fabrication techniques developed for semiconductor devices. Figure depicts I-V characteristics of mesoscopic mesa structures containing 12 Josephson junctions. Each branch among 12 voltage branches seen in the figure corresponds with switching from superconducting state to resistive state of an atomic scale Josephson junction. This is a striking example of the direct observation of capabilities of integrated functional materials.

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