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.
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.
Quantum Hall in topological semimetal
- Quantum Hall states observed in thin films of Dirac semimetal Cd3As2
M. Uchida, Y. Nakazawa, S. Nishihaya, K. Akiba, M. Kriener, Y. Kozuka, A. Miyake, Y. Taguchi, M. Tokunaga, N. Nagaosa, Y. Tokura, and M. Kawasaki
Nature Communications 8, 2274 (2017). Selected for Editors' Highlights
- Gate-tuned quantum Hall states in Dirac semimetal (Cd1−xZnx)3As2
S. Nishihaya, M. Uchida, Y. Nakazawa, M. Kriener, Y. Kozuka, Y. Taguchi, and M. Kawasaki
Science Advances 4, eaar5668 (2018).
- Enhancement of spin-orbit coupling in Dirac semimetal Cd3As2 films by Sb-doping
Y. Nakazawa, M. Uchida, S. Nishihaya, M. Ohno, S. Sato, and M. Kawasaki
Physical Review B 103, 045109 (2021).
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.
Chiral zero mode transport
- Quantized surface transport in topological Dirac semimetal films
S. Nishihaya, M. Uchida, Y. Nakazawa, R. Kurihara, K. Akiba, M. Kriener, A. Miyake, Y. Taguchi, M. Tokunaga, and M. Kawasaki
Nature Communications 10, 2564 (2019).
- Molecular beam epitaxy of three-dimensionally thick Dirac semimetal Cd3As2 films
Y. Nakazawa, M. Uchida, S. Nishihaya, S. Sato, A. Nakao, J. Matsuno, and M. Kawasaki
APL Materials 7, 071109 (2019). Selected for Featured Article
- Intrinsic coupling between spatially-separated surface Fermi-arcs in Weyl orbit quantum Hall states
S. Nishihaya, M. Uchida, Y. Nakazawa, M. Kriener, Y. Taguchi, and M. Kawasaki
Nature Communications 12, 2572 (2021).
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.
Novel magnetic topological materials
- Ferromagnetic state above room temperature in a proximitized topological Dirac semimetal
M. Uchida, T. Koretsune, S. Sato, M. Kriener, Y. Nakazawa, S. Nishihaya, Y. Taguchi, R. Arita, and M. Kawasaki
Physical Review B 100, 245148 (2019).
- Quantum transport observed in films of the magnetic topological semimetal EuSb2
M. Ohno, M. Uchida, R. Kurihara, S. Minami, Y. Nakazawa, S. Sato, M. Kriener, M. Hirayama, A. Miyake, Y. Taguchi, R. Arita, M. Tokunaga, and M. Kawasaki
Physical Review B 103, 165144 (2021).
- Molecular beam deposition of a new layered pnictide with distorted Sb square nets
M. Ohno, M. Uchida, Y. Nakazawa, S. Sato, M. Kriener, A. Miyake, M. Tokunaga, Y. Taguchi, and M. Kawasaki
APL Materials 9, 051107 (2021). Selected for Featured Article, Featured in Scilight
- Maximizing intrinsic anomalous Hall effect by controlling the Fermi level in simple Weyl semimetal films
M. Ohno, S. Minami, Y. Nakazawa, S. Sato, M. Kriener, R. Arita, M. Kawasaki, and M. Uchida
Physical Review B 105, L201101 (2022).
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.
Exotic superconductor films and junctions
- Molecular beam epitaxy growth of superconducting Sr2RuO4 films
M. Uchida, M. Ide, H. Watanabe, K. S. Takahashi, Y. Tokura, and M. Kawasaki
APL Materials 5, 106108 (2017).
- Anomalous enhancement of upper critical field in Sr2RuO4 thin films
M. Uchida, M. Ide, M. Kawamura, K. S. Takahashi, Y. Kozuka, Y. Tokura, and M. Kawasaki
Physical Review B 99, 161111(R) (2019).
- Characterization of Sr2RuO4 Josephson junctions made of epitaxial films
M. Uchida, I. Sakuraba, M. Kawamura, M. Ide, K. S. Takahashi, Y. Tokura, and M. Kawasaki
Physical Review B 101, 035107 (2020).
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.
Quantum transport in correlated topological phases
- Topological Properties and Functionalities in Oxide Thin Films and Interfaces
M. Uchida and M. Kawasaki
Journal of Physics D: Applied Physics 51, 143001 (2018).
- Superconductivity in uniquely strained RuO2 films
M. Uchida, T. Nomoto, M. Musashi, R. Arita, and M. Kawasaki
Physical Review Letters 125, 147001 (2020). Selected for Editors’ Suggestion, Featured in Physics