Uchida Lab

Research

The Uchida Lab conducts research on quantum transport, such as anomalous Hall response, quantum Hall states, and exotic superconductivity, 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, Institute of Science Tokyo. For joining as a graduate student, please take entrance examination of the Department of Physics, Institute of Science Tokyo. Besides, for international students, Institute of Science Tokyo 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.

Novel Off-Diagonal Transport Responses

The Hall effect has traditionally been understood as a transport response proportional to the out-of-plane component of a magnetic field or magnetization, on the basis of a diagonal and linear response paradigm. By contrast, we have recently observed an anomalous Hall effect induced by an in-plane magnetic field. In this effect, a quantum geometric quantity known as orbital magnetization emerges through spin-orbit coupling, independently of spin magnetization, thereby realizing a novel off-diagonal transport response between the magnetic field and the Hall resistivity vector. Motivated by this discovery of the in-plane anomalous Hall effect, we aim to develop new off-diagonal transport responses and achieve their systematic understanding through symmetry-based materials exploration and quantitative experimental investigations.

Magnetotransport governed by quantum geometry

In semimetals characterized by small Fermi surfaces, transport properties are expected to be predominantly governed by quantum geometric effects, exemplified by Berry curvature. The successful growth of high-quality thin films of magnetic topological Weyl semimetals has enabled experimental clarification that such quantum geometric effects appear not only in the Hall response but also in diverse magnetotransport phenomena, including magnetoresistance. Furthermore, it has been recognized that quantum geometric effects can be systematically examined even in nonmagnetic semimetals by focusing on transport components that vary with magnetic field direction. Through these studies, we are pursuing the development of a comprehensive understanding of novel magnetic transport responses governed by quantum geometry.

Superconductivity by thin-film engineering

Even for materials that behave as ordinary metals or insulators in bulk crystal form, superconductivity can emerge in thin-film form, enabled by epitaxial strain or carrier doping from the substrate. A rutile-type ruthenium oxide is among the materials in which superconductivity has recently been discovered through such thin-film engineering, and this material has attracted growing interest also from the viewpoints of magnetic ordering and spintronic functionality. Giant epitaxial strain is expected to significantly modify electronic and phonon band structures, and with examining these strain-induced changes, we are advancing studies of superconducting pairing symmetry.

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 originating 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 arsenide films, suggesting the possibility 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 materials, where magnetic order gives rise to topological electronic states, have the potential to host novel magnetic topological phases through systematic control of their ordered states and symmetries. Understanding these phases critically relies on investigations of magnetic transport phenomena in thin films, which allow flexible tuning of both magnetic order and carrier concentration. Moreover, epitaxial stabilization using suitable substrates allows the synthesis of topological materials that do not exist in bulk crystals. Through the use of these thin-film approaches, we are advancing the exploration of new magnetic topological materials and the clarification of their magnetic transport states.

Exotic superconductor films and junctions

Exotic superconductors with unconventional pairing symmetries, such as topological superconductors hosting Majorana quasiparticles, represent one of the most fascinating research subjects in condensed matter physics. However, their low superconducting transition temperatures and extreme sensitivity to disorder have made thin-film junction studies far more challenging than traditional bulk probes such as specific heat and nuclear magnetic resonance. Layered perovskite ruthenates are representative materials whose superconducting symmetry has yet to be conclusively determined, and phase-sensitive junction experiments are considered crucial for resolving this issue. By advancing oxide molecular beam epitaxy growth techniques, we have, for the first time worldwide, succeeded in fabricating superconducting thin films previously thought to be impossible, and are now addressing the determination of superconducting symmetry through thin-film junction-based studies.

Quantum transport in correlated topological phases

Correlated topological phases driven by the interplay between electron correlations and spin-orbit coupling represent a particularly promising frontier in condensed matter physics. Although a wide variety of fascinating topological phases have been theoretically proposed for iridium and ruthenium oxides with strong spin-orbit coupling, experimental verification and understanding remain limited. Meanwhile, oxide molecular beam epitaxy growth techniques targeting high-melting-point materials such as iridium and ruthenium have achieved significant advances in recent years. On the basis of these techniques, we design and fabricate high-quality epitaxial thin films and artificial heterostructures of strongly correlated oxides, and seek to deepen the understanding of correlated topological phases through high-precision quantum transport measurements.