Condensed Matter Experiment Ⅱ

Solid-State Quantum Transport


Professor : Yoshiro Hirayama
Associate Professor : Go Yusa
Assistant Professor : Katsushi Hashimoto Mohanmad Hamzah Fauzi Toru Tomimatsu Takashi Kobayashi


Example of semiconductor nanostructure: vertically-coupled quantum point contact.

 In the area of quantum semiconductor physics, interesting research has been progressing based on semiconductor hetero- and nano-structures with the concept of carrier interaction. It has been found that two-dimensional systems show fruitful quantum Hall properties depending on orbital, spin and valley degrees of freedom. We are also studying semiconductor nanostructures, such as quantum wires and quantum point contacts. A vertcally-coupled quantum point contact allows us electrical control of coupling characteristics between low-dimensional electron systems. It is interesting to study carrier interactions in these nanostructures. Recently, it has been found that nuclear spins play an important role under certain quantum Hall conditions. Coherent control of nuclear spins was demonstrated in a semiconductor nanodevice. Nuclear spin relaxation and NMR spectrum measurement were used as a sensitive detector to study electron spin features in semiconductor quantum structures. Interaction between photons and nuclear spins via electron spins will be realized by using a combination of optical and electrical methods. NMR and MRI have been widely used in chemistry and medical science, and their extension to solid-state physics may open a way to novel spintronics including nuclear spins. Our studies of semiconductor quantum systems have resulted in the coherent control of carriers, spins, and nuclear spins, and represent fundamental advances toward quantum computers. These studies will be carried out in collaboration with NTT Basic Research Laboratories where world-class knowledge and technologies have been accumulated for crystal growth, nano-processing and semiconductor physics.

Spin phase transition at n = 2/3 and resistively-detected NMR.

Dilution refrigerator.
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