Browsing by Author "Ochiai, Y."

Now showing 1 - 5 of 5

Enhanced Phase Relaxation in a Hybrid Ferromagnet/Semiconductor System
(2009-07-01)
Chen, Kuang Yao
;
Yang, Chun-Kai
;
Liang, C. -T.
;
Aoki, N.
;
Ochiai, Y.
Hybrid ferromagnet/semiconductor systems have been the focus of considerable attention because of the transport properties of two-dimensional electron systems and their potential applications to magnetic storage and sensing devices. We use the weak localization effect to probe the dephasing mechanism at low temperatures. In our study, the zero-temperature phase-relaxation rate can be enhanced in a hybrid ferromagnet/semiconductor system, which may he due to the inhomogeneous magnetic field emanating from the Ni film. The result may improve understanding of the issue of zero-temperature dephasing in disordered systems.
Probing Insulator-quantum Hall Transitions by Current Heating
(2009-07-01)
Chen, Kuang Yao
;
Liang, C. -T.
;
Aoki, N.
;
Ochiai, Y.
;
Cheng, K. A.
We report a magneto-transport study on the two-dimensional electron system (2DES) in an AlGaAs/GaAs heterostructure. The direct insulator to quantum Hall conductor transition is observed at low temperatures by increasing the magnetic field B perpendicular to the 2DES. We can also observe the transition by varying the current I and find a relation T(e) similar to I(a) between electron effective temperature T(e) and current. Here, a denotes the exponent for the power law. The exponent a, however, can have different values on the two sides of the transition point, which indicates different inelastic scattering mechanisms in the low-field insulator and in the quantum Hall conductor.
Probing Landau quantization with the presence of insulator-quantum Hall transition in a GaAs two-dimensional electron system
(2008-07-23)
Chen, Kuang Yao
;
Chang, Y. H.
;
Liang, C-T
;
Aoki, N.
;
Ochiai, Y.
Magneto-transport measurements are performed on the two-dimensional electron system (2DES) in an AlGaAs/GaAs heterostructure. By increasing the magnetic field perpendicular to the 2DES, magneto-resistivity oscillations due to Landau quantization can be identified just near the direct insulator-quantum Hall (I-QH) transition. However, different mobilities are obtained from the oscillations and transition point. Our study shows that the direct I-QH transition does not always correspond to the onset of strong localization.
Probing the onset of strong localization and electron-electron interactions with the presence of a direct insulator-quantum Hall transition
(2010-10-01)
Lo, Shun-Tsung
;
Chen, Kuang Yao
;
Lin, T. L.
;
Lin, Li-Hung
;
Luo, Dong-Sheng
We have performed low-temperature transport measurements on a disordered two-dimensional electron system (2DES). Features of the strong localization leading to the quantum Hall effect are observed after the 2DES undergoes a direct insulator-quantum Hall transition on increasing the perpendicular magnetic field. However, such a transition does not correspond to the onset of strong localization. The temperature dependences of the Hall resistivity and Hall conductivity reveal the importance of the electron-electron interaction effects for the observed transition in our study. (C) 2010 Elsevier Ltd. All rights reserved.
Probing the onset of strong localization and electron-electron interactions with the presence of a direct insulator-quantum Hall transition
(2010-10-01)
Lo, Shun-Tsung
;
Chen, Kuang Yao
;
Lin, T. L.
;
Lin, Li-Hung
;
Luo, Dong-Sheng
We have performed low-temperature transport measurements on a disordered two-dimensional electron system (2DES). Features of the strong localization leading to the quantum Hall effect are observed after the 2DES undergoes a direct insulator-quantum Hall transition on increasing the perpendicular magnetic field. However, such a transition does not correspond to the onset of strong localization. The temperature dependences of the Hall resistivity and Hall conductivity reveal the importance of the electron-electron interaction effects for the observed transition in our study. (C) 2010 Elsevier Ltd. All rights reserved.