| 研究実績の概要 |
In the last year of the project, we have established experimentally the techniques that we developed theoretically in previous years. Notably, we demonstrated how the geometrical shape of a quantum dot can be reconstructed using high magnetic field measurements. It verifies inventing a new spectroscopic method, not available before. The method allowed us to observe an electron spin relaxation assisted by nuclear spins. Such a relaxation process has been predicted theoretically already 16 years ago, but up to know never confirmed experimentally. We have succeeded in overcoming difficulties related to the extreme requirements on the sample stability (experimental) as well as to the separation of subtle effects due to the spin-orbit interaction from the interactions with nuclear spins (theoretical). As a by-product of that experiment, we reported the current world record of the electronic spin lifetime in a gated nanostructure, being almost 1 minute long. These results are a significant advancement in the field of gated quantum dot spin qubits.
Besides, we also observed a puzzling difference between the spin and charge dynamics in a charged quantum dot. Namely, in certain dot configurations, the spin information lifetime is much longer than the charge lifetime, even though the spin state is physically not separable from its electronic carrier. We have explained these observations in theory.
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