NSF Award
2428579
Non-technical abstract:<br/>The research focuses on the development and understanding of a novel type of quantum devices, the “multiterminal Josephson junctions”. Conventionally, Josephson junctions are made of two superconductors – materials in which electric current can flow without resistance – connected through a non-superconducting region. The principal investigator’s team has recently made Josephson junctions with several superconducting regions connected together. The breakthrough became possible by making the non-superconducting region from graphene – a single atomic monolayer of graphite. Graphene is known to be ballistic – in can conduct electrons over large distances without scattering – enabling efficient coupling between multiple superconducting terminals. The project enhances understanding of the multiterminal Josephson junctions, which are both expected to have fascinating physical properties and may eventually find applications in future quantum devices. The research also contributes to training of students on all levels in quantum nanotechnology. The project includes outreach in the local community, with a special focus on broadening the participation of underrepresented groups in STEM.<br/><br/>Technical abstract:<br/>This project builds on the recent progress achieved by this research team and other groups in making multi-terminal Josephson junctions. One of the central themes of this work is the analogy between the Andreev bound states in a multiterminal Josephson junction and the band structure of a crystal. In particular, it has been predicted that multiterminal Josephson junction could be used to emulate topologically nontrivial bands containing Weyl points. These bands can be explored to search for the predicted topological signatures, such as the quantized transconductance. The project further aims to look for the predicted topological contributions to the multiplet resonances. Finally, the team plans to explore the physics of the “Josephson triode” – a tunable superconducting diode recently realized in this type of samples – with a particular focus on its topological properties. Multi-terminal Josephson junctions have been touted as “synthetic topological matter” which should offer new insights into the role of topology in condensed matter systems. The project intends to enhance our understanding of these structures, which is relevant to a whole class of hybrid superconductors samples. The multi-terminal Josephson junctions are both expected to have fascinating physical properties and may eventually find applications in quantum microwave devices.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
