Superconducting effects in the quantum Hall regime
Inducing superconducting correlations in the topologically protected edge states. This research is inspired by the search for the topologically protected qubits.
Multi-terminal Josephson junctions
Exploring complex phase dynamics in graphene-based multi-terminal Josephson junctions and Josephson circuits, via both experiment and simulation.
Superconductivity at the complex oxide Interfaces
Exploring superconducting mechanisms in novel materials, and looking for their application in superconducting electronics and computation.
Qubits and high frequency measurements
Characterizing and designing qubits in novel systems using high-frequency measurements and providing RF drive to explore Josephson junction behaviors through Shapiro steps.
Our main research direction is combining superconductivity and the quantum Hall effect (QHE). These two phenomena have been long viewed as mutually exclusive, since the high magnetic field in the quantum Hall regime destroys the time-reversal symmetry required for superconductivity. We have studied superconductivity induced in the quantum Hall state in graphene in a series of works (Amet et al., 2016, Seredinski et al., 2019, Zhao et al., 2020, and Zhao et al., 2023). The hybrid QHE-superconductor devices are also predicted to host Majorana fermions which may be used for constructing qubits for fault tolerant quantum computation.
The second area of research is in multi-terminal devices. These novel structures are predicted to enable many new physics concepts, such as emulating band structures of topological materials and entangling pairs of Cooper pairs (quartets). We have made the first multi-terminal Josephson junctions in ballistic graphene, and have investigated their dynamics (Arnault et al., 2022, Arnault et al., 2024). Additionally, we utilized one of these devices to engineer a superconducting diode with 100% efficiency at zero magnetic field (Chiles et al., 2023). We are interested to further develop multi-terminal Josephson junctions in pursuit of a wide range of non-equilibrium and topological effects.
Additionally, we have added high frequency lines to our fridges, enabling measurements in the MHz and GHz regimes. We used the MHz setup to measure thermal properties of QHE-superconductor interfaces (Zhao et al., 2024) and plan to expand these techniques to measurements of thermal effects in systems not accessible by classic transport measurements. Meanwhile, the GHz setup enables us to measure superconducting qubits, as demonstrated by measurements performed on niobium transmons. We plan to expand the use of this setup to include qubits in novel superconducting systems which could provide kinetic inductance and dielectric properties well suited for RF qubits and aid in eliminating losses at material interfaces.
1D and 0D research in our group focuses on quantum dots made in graphene and carbon nanotubes. In nanotube quantum dots, we have studied the role of dissipative environment in quantum tunneling (Mebrahtu et al., 2013). Dissipation is of fundamental importance in quantum mechanics and is responsible for the transition to the classical behavior. We have been studying quantum phase transitions, Majorana fermions, and other novel states of matter in this system.
The links above expand on these areas of interest for the Finkelstein group.
