Nano-Hybrid Josephson Junctions: Its applications and future of Various Nanostructures
Recent advances in nanofabrication techniques, however, have enabled the fabrication of hybrid quantum devices of superconductors and nanostructures (such as nanowires, carbon nanotube, and graphene), the Josephson coupling energy of which can be tuned electrically by the application of the gate voltage. We observed the macroscopic quantum tunnelling (MQT) of a Josephson phase particle, which exhibits a crossover from the classical to quantum regime, in a superconductor-graphene-superconductor (SGS) Josephson junction. Most importantly, the crossover temperature was controlled with the gate voltage, implying that the discrete energy level of a phase particle is also gate-tunable and a new class of quantum device such as a gate-tunable phase quantum bit (qubit) would be possible utilizing the MQT behaviour of the SGS junctions. We believe that our results demonstrate a powerful new approach in the controllability of macroscopic quantum states in a Josephson junction, and can be readily generalized for other nanostructures, including semiconductor nanowires and carbon nanotubes. Ultimately, this will be a key step toward developing a nanostructure-based superconducting qubits.
* 일시 : 2011년 3월 31일 목요일 오후 4시 30분
* 장소 : 베어드홀 103호
* 연사 : 도 용 주 교수 (고려대 디스플레이·반도체물리학과)