Asia Pacific Physics Week 2024 (APPW2024)

Wednesday, Nov. 6, 2024 

3:00 PM - 3:30 PM  C. N. Yang Award Talk  Gil-Ho Lee (Pohang University of Science and Technology) 

Engineering Andreev band in graphene Josephson junctions

Gil-Ho Lee

Department of Physics, POSTECH, South Korea

Andreev bound states (ABS), which form in proximity Josephson junctions, govern the physics of the Josephson devices. Consequently, understanding and manipulating the ABS is essential for optimizing device functionality. In this regard, two topics will be discussed; one is Floquet physics of ABS, and another is ABS of multi-terminal Josephson junction.

First, we will introduce the generation of steady Floquet Andreev (F-A) states in graphene Josephson junctions by continuous microwave application and direct measurement of their spectra by superconducting tunnelling spectroscopy. This can be a unique platform to study non-equilibrium quantum physics at a device level.

Second, we will discuss the artificial topological band structure of three-terminal graphene Josephson junctions by using superconducting tunneling spectroscopy. We controlled the superconducting phase configurations by applying the flux gates and obtained the ABS energy spectrum as a function of two independent phase differences and energy. Such quasi-momentum v.s. energy map of ABS unveils the transition between gapped and gapless states, corresponding to the topological band structure of 2D-Dirac semimetals.