Visualizing hidden states in Josephson junctions

Shaowen Chen

Harvard University (Yacoby group)

Wednesday, September 20

2:00 pm ET/11:00 am PT

Abstract:

Electrical resistance measurement is a widely used and effective method to characterize topological and correlated phases in quantum materials. However, resistance measurements have limitations – they average over distances given by the contact separation and are therefore insensitive to features smaller than the size and spacing of the electrical contacts. Additionally, they are incapable of providing details in cases where the underlying resistance is zero such as superconductors. To circumvent these limitations, local mapping of current flow can be used to uncover hidden phases in exotic materials. In this talk I will present recent results of current flow patterns in a Josephson junction using nitrogen vacancy (NV) centers in diamond. Our measurements reveal intricate current flow patterns that change rapidly as the external flux or DC current are varied. Our results uncover ground state configurations that can be switched with subtle changes in the drive current, and provide insight to the origin of the superconducting diode effect. Our observed current changes to the current flow patterns are invisible in a conventional transport experiment thus highlighting the importance of our imaging capabilities. 

Bio:

Shaowen Chen is a Harvard quantum initiative postdoctoral fellow working in the Yacoby group. He is interested in studying correlated and topological properties of quantum materials using electrical transport and novel quantum sensors. Shaowen obtained his B.S. in Physics from Peking University, and Ph.D. in applied physics from Columbia University in the Dean group.