- 著者
- Tomimoto Shinichi Kurokawa Atsushi Sakuma Yoshiki Usuki Tatsuya Masumoto Yasuaki
- 出版者
- American Physical Society
- 雑誌
- Physical review B (ISSN:10980121)
- 巻号頁・発行日
- vol.76, no.20, pp.205317, 2007-11
- 被引用文献数
- 14 10
Recombination dynamics of excitons confined in disk-shaped InAs/InP quantum dots is studied by time-resolved photoluminescence measurements. By comparing the result with that in a homologous ultrathin quantum well, it is revealed that the lateral confinement of excitons suppresses the thermal variation of the radiative recombination lifetime. The oscillator strength of the radiative transition is reduced with the decrease of the disk height, which is attributed to the increasing tunneling into the InP barrier of the exciton wave function.
- 著者
- Tomimoto Shinichi Nozawa Shinsuke Terai Yoshikazu Kuroda Shinji Takita Kôki Masumoto Yasuaki
- 出版者
- The American Physical Society
- 雑誌
- Physical review B (ISSN:10980121)
- 巻号頁・発行日
- vol.81, no.12, pp.125313, 2010-03
- 被引用文献数
- 11
We have studied the spin dynamics of confined electrons in an ultrathin CdTe/ZnTe quantum well andself-assembled quantum dots by time-resolved Kerr-rotation technique. The dependence of the spin-precessionfrequency on the magnetic field direction shows the anisotropy of the g-factor tensor, which is the opposite ofthe usual quantum wells with moderate widths. The geometrical anisotropy of the confinement also affects theinitial orientation of the electron spins created optically, as revealed clearly with the use of oblique-incidencepump pulses.
- 著者
- Tomimoto Shinichi Kawana Keisuke Murakami Akira Masumoto Yasuaki
- 出版者
- Elsevier B.V.
- 雑誌
- Journal of Luminescence (ISSN:00222313)
- 巻号頁・発行日
- vol.133, pp.162-168, 2013-01
- 被引用文献数
- 1
We have experimentally observed the spin polarization process of single electrons in InP/InGaP quantum dots by time-resolved Kerr rotation measurements. It is found that the inversion of the spin polarization direction occurs with the variation of the intensity of the optical pulse. The spin coherence lifetime abruptly changes on the occurrence of the inversion. We have reproduced the inversion in numerical simulations using the density operator of the electron–trion four-level system, assuming a small deviation of the optical pulse from circular polarization. The change of the spin lifetime is attributed to the qualitative change of the four-level system in the electric polarization state.
- 著者
- Tomimoto Shinichi Saito Shingo Suemoto Tohru Takeda Jun Kurita Susumu
- 出版者
- American Physical Society
- 雑誌
- Physical review B (ISSN:01631829)
- 巻号頁・発行日
- vol.66, no.15, pp.155112, 2002
- 被引用文献数
- 52
The temporal evolution of the photoexcited state in quasi-one-dimensional (1D) halogen-bridged platinum complexes [Pt(en)2][Pt(en)2X2](ClO4)4 (abbreviated as Pt-X, X=Cl, Br or I), has been comprehensively studied by femtosecond time-resolved luminescence spectroscopy. In Pt-Cl, new short-lived hot luminescence is found in the low-energy side of a self-trapped exciton (STE) luminescence band. The overall behavior of the STE luminescence band within 2 ps is well explained by the vibrational relaxation of the STE. The behavior is reproduced by a model calculation based on wave packet propagation on an interaction mode composed of frequency-dispersed bulk phonons. This model is also applied to the previous results in Pt-Br. For both Pt-Cl and Pt-Br, the frequency spectra of phonons which compose the interaction mode have been estimated. In Pt-I, the STE luminescence decays much faster than those in Pt-Cl and Pt-Br, showing existence of more effective nonradiative decay channel.
- 著者
- Masumoto Yasuaki Yoshida Seitaro Ikezawa Michio Tomimoto Shinichi Sakuma Yoshiki
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.98, no.6, pp.061905, 2011-02
- 被引用文献数
- 5 4
We observed that the biexciton binding energy in InAs quantum rhombic disks (QRDs) is enhanced by twice compared with that for InAs quantum dots (QDs) so far reported around 1.24 μm nearby the telecommunication wavelength. The heterodyne-detected four-wave-mixing detected the exciton-biexciton quantum beat superposed on photon echo decay, giving the biexciton binding energy of 3.4 meV to 3 monolayer (ML) InAs QRDs and 4.1 meV to 4 ML InAs QRDs, respectively. The largest biexciton binding energy of 4.1 meV in InAs QDs is ascribed to increased electron-hole overlap in confined geometry with a minimized strain distribution.
- 著者
- Tomimoto Shinichi Kawana Keisuke Murakami Akira Masumoto Yasuaki
- 出版者
- American Physical Society
- 雑誌
- Physical review B (ISSN:10980121)
- 巻号頁・発行日
- vol.85, no.23, pp.235320, 2012-06
We have experimentally studied the spin dynamics of excitons, electrons, and trions in charge-tunable InP/InGaP quantum dots (QDs) excited by picosecond resonant laser pulses by observing the time-resolved Kerr rotation. In singly charged QDs, inversion of the spin polarization direction of doped electrons is found to be caused simply by variation in the pulse intensity, which is accompanied by an abrupt change of the spin coherence time. This phenomenon is reproduced by density-matrix calculations allowing for the reaction on the QD electron-trion four-level system during its coherent radiation emission. This result means that the optical coherence is another critical factor affecting electron spin coherence.