Formation of electrically defined quantum dots and the observation of quantum many-body effects in zinc oxide

As fundamental structures in quantum devices, semiconductor quantum dots have primarily been developed using materials like gallium arsenide and silicon. These materials have enabled the creation of highly controllable, electrically defined quantum dots applied in fields such as quantum computing. However, recent technological advancements have now enabled the fabrication of high-quality heterostructures with zinc oxide, although electrically defined quantum dots had yet to be achieved in this material. A research team has now successfully created an electrically defined quantum dot from a zinc oxide heterostructure. By adjusting the voltage controlling the quantum dot’s internal states, they were able to measure the Coulomb diamond—a distinctive quantum dot state diagram. Analysis of this diamond structure further allowed them to evaluate the orbital energy resulting from quantum confinement effects. In addition, they observed a novel phenomenon in zinc oxide quantum dots: the Kondo effect, a quantum many-body effect manifesting independently of electron number. The unique temperature and magnetic field dependencies observed, distinct from those of conventional materials, are likely due to the strong electron correlation inherent in zinc oxide. These findings lay the groundwork for new quantum devices based on advanced materials like zinc oxide, whose unique spin coherence and electron correlation are anticipated to be valuable for next-generation quantum technologies.

Papers

Journal: Nature Communications

Title: Parity-independent Kondo effect of correlated electrons in electrostatically defined ZnO quantum dots

Authors: Kosuke Noro, Yusuke Kozuka, Kazuma Matsumura, Takeshi Kumasaka, Yoshihiro Fujiwara, Atsushi Tsukazaki, Masashi Kawasaki and Tomohiro Otsuka*

DOI: 10.1038/s41467-024-53890-2