|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.
- Plasmon transport in graphene or 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
- 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).
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.
- 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).
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).
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).
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