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I am interested in many-body physics in two-dimensional electron systems (2DESs).
In particular, I investigate electron spin states in a quantum Hall system by resistively-detected nuclear magnetic resonance.
Recently, I started research on plasmon transport in GaAs/AlGaAs 2DESs or graphene using time-resolved transport measurement.
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- Plasmon transport in graphene and GaAs/AlGaAs 2DESs
- Quantum Hall effect
- Bilayer quantum Hall state at nu=1
- Bilayer quantum Hall state at nu=2
- Bilayer quantum Hall state at nu=2/3
- Control of nuclear spins in semiconductors
clear
- Electric Field Induced Nuclear Spin Resonance Mediated by Oscillating Electron Spin Domains in GaAs-Based Semiconductors
N. Kumada, T. Kamada, S. Miyashita, Y. Hirayama, T. Fujisawa
Phys. Rev. Lett. 101, 137602 (2008).
Abstract--
We demonstrate an alternative nuclear spin resonance using radio frequency (RF) electric field
(nuclear electric resonance: NER) instead of magnetic field.
The NER is based on the electronic control of electron spins forming a domain structure.
The RF electric field applied to a gate excites spatial oscillations of the domain walls
and thus temporal oscillations of the hyperfine field to nuclear spins.
>>further information
- Decoherence of nuclear spins due to dipole-dipole interactions probed by resistively detected nuclear magnetic resonance
T. Ota, G. Yusa, N. Kumada, S. Miyashita, T. Fujisawa, and Y. Hirayama
Appl. Phys. Lett. 91, 193101 (2007).
Abstract--
We study decoherence of nuclear spins in a GaAs quantum well structure using resistively detected NMR.
In a tilted magnetic field, the decoherence is enhanced by the direct dipole-dipole interactions between
first nearest-neighbor nuclei.
The results agree well with simple numerical calculations.
- Nuclear spin population and its control toward initialization using an all-electrical sub-micron scale nuclear magnetic resonance device
T. Ota, G. Yusa, N. Kumada, S. Miyashita, and Y. Hirayama
Appl. Phys. Lett. 90, 102118 (2007).
Abstract--
We study the nuclear spin population in a GaAs quantum well structure and demonstrate its initialization
using an all-electrical NMR device.
- Effects of inversion asymmetry on electron-nuclear spin coupling in semiconductor heterostructures: A possible role of spin-orbit interactions
K. Hashimoto, K. Muraki, N. Kumada, and Y. Hirayama
Phys. Rev. Lett. 94, 146601 (2005).
Abstract--
We show that electron-nuclear spin coupling in semiconductor heterostructures is strongly
modified by their potential inversion asymmetry.
We suggest that even a very weak Rashba spin-orbit interaction can play a dominant role.
- Other topics
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