Study Results

Here, we show the main research results obtained in Hirayama-group after Prof. Hirayama’s movement to Tohoku University at 2006. We will add new results and missing items in the future.

We have promoted researches on carrier interactions in semiconductors, especially putting emphasis on interaction with nuclear spins. We have developed highly-sensitive resistively-detected NMR based on electron spin / nuclear spin interactions atν=2/3 and applied this technique to various studies. The outline of these studies can be found in,

• Electron spin/ nuclear spin interactions at ν=2/3 and dynamic nuclear polarization

  （ SpinInteractionTwoThird.pdf： 313 KB）

• Resistively-detected highly-sensitive NMR

  （ RDNMRprinciple.pdf： 349 KB）

The research results as an extension of these studies can be seen in,

• Nuclear spin diffusion in double quantum wells

  （ Nucleardiffusion.pdf： 240 KB）

• Many-body interaction between nuclear spins and electron spins with Nambu-Goldstone mode

  （ Dickesuper.pdf： 218 KB）

• Optically pumped nuclear polarization and its resistive detection

  （ Opticalnuclearpol.pdf： 255 KB）

The nuclear polarization and detection can be achieved by using quantum Hall breakdown, too. We use this technique in,

• Electric field mediated nuclear spin resonance

  （ NER.pdf： 233 KB）

to extend the measurable range in nuclear resonance experiments. The resistively-detected NMR (RDNMR) can be applied also for nanostructure such as quantum point contact (QPC). Examples are.

• RDNMR in GaAs quantum point contacts (QPCs)

  （ FundamentalFeatureAtNu=2.pdf： 159 KB）

Microscopic studies based on nanoprobe are also very important.

• Real Space Observation of a Quantum Hall Transition by STM

  （ QHESTMobservation.pdf： 159 KB）

is an example of the output of such a research. We have promoted research on InSb systems as shown below,

• Highly-sensitive resistively-detected NMR of InSb two-dimensional systems

  （ InSbRDNMR.pdf： 366 KB）

• Fundamental physics of nuclear polarization clarified by using the simplest quantum Hall ferromagnet at ν = 2

  （ RDNMRQPC.pdf： 366 KB）

• Gate control of InSb quantum wells with ALD gate dielectrics

  （ InSbGatecontrol.pdf： 224 KB）

As a fundamental research of low-dimensional physics and nanostructure devices, we have the following outputs.

• Valley control in Si 2D electrons and its effect on 2D physics

  （ valleyfreedom.pdf： 226 KB）

• Various studies on quantum point contacts (QPCs)

  （ QPChomepagever2.pdf： 253 KB）

The coherent characteristics of spin systems induced by a pulse sequence are interesting as a novel nuclear resonance technique.

• Measurement of the noise spectrum using a multiple-pulse sequence

  （ generalizedT2.pdf： 226 KB）