Research

Quantum Hall effect Interference

Quantum interferometers are powerful tools for probing the wave-nature and exchange statistics of indistinguishable particles. Of particular interest are interferometers formed by the chiral, one dimensional (1D) edge channels of the quantum Hall effect (QHE) that guide electrons without dissipation. Using quantum point contacts (QPCs) as beam-splitters, these 1D channels can be split and recombined, enabling interference of charged particles. Such quantum Hall interferometers (QHIs) can be used for studying exchange statistics of anyonic quasiparticles.

In this line of research, we are developing a robust QHI fabrication technique in van der Waals (vdW) materials, for example, Fabry-Pérot (FP). By careful heterostructure design, we are able to measure pure Aharonov-Bohm (AB) interference effect in the integer QHE, a major technical challenge in finite size FP interferometers. Our QHI with tunable QPCs presents a versatile platform for interferometer studies in vdW materials and enables future experiments in the fractional QHE.

Parafermion research

Topological superconductors represent a phase of matter with nonlocal properties which cannot smoothly change from one phase to another, providing a robustness suitable for quantum computing. Substantial progress has been made towards a qubit based on Majorana zero modes (MZM), whose exchange (braiding) produces topologically protected logic operations. However, because braiding MZMs does not offer a universal quantum gate set, Majorana qubits are computationally limited. This drawback can be overcome by introducing parafermions, a novel generalized set of non-Abelian modes. The primary route to synthesize parafermions involves inducing superconductivity in the fractional quantum Hall (fqH) edge.

In this line of research, we use high-quality graphene-based van der Waals devices with narrow superconducting niobium nitride (NbN) electrodes, in which superconductivity and robust fqH coexist. In our previous study we found crossed Andreev reflection (CAR) across the superconductor separating two counterpropagating fqH edges which demonstrates their superconducting pairing. These results provide a route to realize novel topological superconducting phases with universal braiding statistics in fqH-superconductor hybrid devices.

Twistronics

The recent discovery of correlated insulator states, superconductivity and the quantum anomalous Hall effect in moiré superlattices has sparked a new field which is known today as Twistronics. Moiré superlattices are created by stacking of van der Waals heterostructures with a controlled twist angle which enables the engineering of electron band structure. This unique degree of freedom enables to reduce the energy bandwidth of electrons compared to the long-range Coulomb interaction energy thereby promoting correlated effects. In this line of research, we intend to probe these many body physics phenomena and uncover its origin and properties by utilizing shot noise as well as Josephson interferometry techniques.