A research team from POSTECH realized short clearance ballistic Josephson junction, which had existed only in theory.
A joint research team of Professor Lee Hu-jong from POSTECH’s Dept. of Physics, Dr. Lee Gil-hu, Professor Ji Seung-hun and Kim Sol in doctorate course announced on the 2nd that it had implemented short clearance ballistic Josephson junction in a vertical shape by sandwiching graphene in between two superconductive electrodes as the first in the world.
Josephson junction refers to a phenomenon of current flowing without heat generation when a thin metallic material is inserted in between superconductive membranes even though the superconductors do not touch one another. Superconductor has a characteristic of letting current flow without generating heat. Therefore, it is used widely in electrical and electronic fields.
Josephson junction triggers quantum interference, and thus is applied to studies on quantum computer, which is called high-tech computer of the future, quantum interference devices using the phenomenon of quantum interference and extra high frequency oscillating devices.
It has been predicted only in theory that, when the metal inserted in between superconductors becomes extremely thin, short clearance ballistic Josephson junction of strong quantum coherence can be generated. However, despite various studies conducted for decades, short clearance ballistic Josephson junction was not achieved in reality. This is because it was difficult to make the thickness of high-purity metallic layer in between superconductors small in atomic unit.
The research team took note of graphene, the ‘dream material,’ as a solution. Graphene, which is a carbon atom, has thickness equivalent to that of a single atom. Therefore, it is known to be the thinnest conductor in existence.
As a result of inserting graphene in between superconductive electrodes, the research team verified not only current limit, which is observed with short clearance ballistic Josephson junction, but also the expected quantum characteristics.
Professor Lee Hu-jong expressed anticipation, “This study outcome will be applied widely to graphene – superconductive quantum device development in addition to atomic unit device structure control.”
The outcome of this study, which had been conducted with support from Global Frontier R&D Project and Leading Research Center Support Project of National Research Foundation of Korea, was published in the latest issue of the Nature Communications.