Uchida Lab

Research

The Uchida Lab conducts research on quantum transport emerging in extremely clean systems, such as exotic superconductivity and quantum Hall states, with producing epitaxial thin films and artificial heterostructures of topological and correlated materials. The following are some of the latest core research projects in our group. Please get in contact with Uchida for details.

• Undergraduate students are accepted in the Department of Physics, Tokyo Tech. For joining as a graduate student, please take entrance examination of the Department of Physics, Tokyo Tech. Besides, for international students, Tokyo Tech offers diverse International Study Programs, such as International Graduate Program. Admission from the doctoral program is also welcomed. Please feel free to contact by email.

• If you are interested in joining as a postdoctoral researcher, please contact by email first. Especially for international researchers, Japan Society for the Promotion of Science offers some Postdoctoral Fellowship Programs.

Quantum Hall in topological semimetal

Various quantum transport phenomena have been proposed in topological Dirac semimetal, which corresponds to the parent phase of topological materials with topologically non-trivial electronic structures. While theoretical research has taken the lead in this field, successful fabrication of extremely high-quality thin films of cadmium arsenide, an ideal topological Dirac semimetal, enables us to study novel transport states originaintg in the three-dimensional Dirac dispersions. We elucidate quantum transport represented by quantum Hall effect, by performing control experiments with film techniques such as electric field effect and chemical substitution.

Chiral zero mode transport

Topological semimetal is predicted to form a characteristic bulk electronic state called chiral zero mode under magnetic fields and exhibit unprecedented conduction composed of the bulk and surface states connected via Weyl points. In fact, conduction of the surface sate and its quantization have been observed in our high-quality cadmium arsenium films, suggesting the possiblity that quantum Hall conduction normally appearing in two-dimensional systems can be extended into three-dimensional systems, where the top and bottom surfaces are connected by the chiral zero mode. We conduct research with the aim of developing a new quantum transport theory based on the chiral zero mode.

Novel magnetic topological materials

Magnetic topological semimetals with localized spin moments are of great interest for exploring novel magnetic topological phases by controlling their magnetic ordering and spatial symmetry. For such magnetic topological phases, research on quantum transport using precisely controllable thin films will be particularly important. Thin films are powerful approaches also to epitaxially stabilize new topological materials which do not exist in the bulk form and to induce magnetization into non-magnetic topological materials by the magnetic proximity effect. We develop new magnetic topological materials and elucidate their quantum transport with utilizing these film techniques.

Exotic superconductor films and junctions

Exotic superconductors consisting of multi-component order parameters, such as topological superconductors hosting Majorana fermions, are attractive research subjects. Due to their low transition temperature and high impurity sensitivity, however, film and junction experiments have fallen far behind other measurement probes. Layered ruthenium oxide Sr₂RuO₄ is a typical superconductor with unknown superconducting symmetry, and junction experiments are considered important for determining it. We have succeeded in fabricating superconducting Sr₂RuO₄ films by refining oxide molecular beam epitaxy techniques, enabling us to study by phase sensitive measurements of film-based junctions.

Quantum transport in correlated topological phases

Correlated topological phases, which emerge depending on the electron correlation and spin-orbit interaction strengths, are a burgeoning research area. Although various intriguing topological phases have been proposed such as for iridium and ruthenium oxides with strong spin-orbit interaction, they have not yet been fully verified by experiments. On the other hand, oxide molecular beam epitaxy techniques using high-melting-point metals including the iridium and ruthenium has significantly improved in the recent years. We elucidate correlated topological phases by measuring quantum transport for these tailored high-quality films and heterostructures.