著者

Yoshimi R. Tsukazaki A. Kozuka Y. Falson J. Takahashi K. S. Checkelsky J. G. Nagaosa N. Kawasaki M. Tokura Y.

出版者

Nature Publishing Group

雑誌

Nature communications (ISSN:20411723)

巻号頁・発行日

no.6, 2015-04-14

---

The three-dimensional topological insulator is a novel state of matter characterized by two-dimensional metallic Dirac states on its surface. To verify the topological nature of the surface states, Bi-based chalcogenides such as Bi2Se3, Bi2Te3, Sb2Te3 and their combined/mixed compounds have been intensively studied. Here, we report the realization of the quantum Hall effect on the surface Dirac states in (Bi1−xSbx)2Te3 films. With electrostatic gate-tuning of the Fermi level in the bulk band gap under magnetic fields, the quantum Hall states with filling factor ±1 are resolved. Furthermore, the appearance of a quantum Hall plateau at filling factor zero reflects a pseudo-spin Hall insulator state when the Fermi level is tuned in between the energy levels of the non-degenerate top and bottom surface Dirac points. The observation of the quantum Hall effect in three-dimensional topological insulator films may pave a way toward topological insulator-based electronics.UTokyo Research掲載「トポロジカル絶縁体の表面ディラック状態の量子化を実証」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/observation-of-quantization-in-surface-dirac-states-of-topological-insulator.html

著者

Tomimoto S. Matsubara M. Ogasawara T. Okamoto H. Kimura T. Tokura Y.

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.98, no.1, pp.017402, 2007-01

被引用文献数

16

---

Optical manipulation of the magnetic anisotropy is demonstrated for bilayered manganites, La2-2xSr1+2xMn2O7, by means of femtosecond Kerr-rotation measurements. Upon the photoexcitation on the x=0.32 crystal, the magnetization exhibits the precessional motion for about 1 ns, revealing the directional change of the magnetocrystalline anisotropy from the c axis to the ab plane. This change of the anisotropy induces the nonthermal decrease of the c-axis magnetization component for about 1 ns.

著者

Tomimoto S. Miyasaka S. Ogasawara T. Okamoto H. Tokura Y.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.68, no.3, pp.035106, 2003

被引用文献数

38 24

---

The photoinduced effect on the orbital-ordered phase in perovskite-type LaVO3 has been investigated by femtosecond time-resolved reflection spectroscopy. Large reflectivity change has been observed immediately after photoirradiation. The spectral shape and polarization dependence of the reflectivity change indicate the melting of the orbital order induced by photoexcitation. The photocarriers annihilate in about 200 fs, and the orbital order partially recovers owing to thermalization with the lattice in 2–4 ps.