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1. Supercurrent in Graphene Josephson Junctions with Narrow Trenches in the Quantum Hall Regime

   https://doi.org/10.1557/adv.2018.469  

   Seredinski, Andrew; Draelos, Anne; Wei, Ming-Tso; Ke, Chung-Ting; Fleming, Tate; Mehta, Yash; Mancil, Ethan; Li, Hengming; Taniguchi, Takashi; Watanabe, Kenji; et al (April 2018, MRS Advances)

   ABSTRACT Coupling superconductors to quantum Hall edge states is the subject of intense investigation as part of the ongoing search for non-abelian excitations. Our group has previously observed supercurrents of hundreds of picoamperes in graphene Josephson junctions in the quantum Hall regime. One of the explanations of this phenomenon involves the coupling of an electron edge state on one side of the junction to a hole edge state on the opposite side. In our previous samples, these states are separated by several microns. Here, a narrow trench perpendicular to the contacts creates counterpropagating quantum Hall edge channels tens of nanometres from each other. Transport measurements demonstrate a change in the low-field Fraunhofer interference pattern for trench devices and show a supercurrent in both trench and reference junctions in the quantum Hall regime. The trench junctions show no enhancement of quantum Hall supercurrent and an unexpected supercurrent periodicity with applied field, suggesting the need for further optimization of device parameters. 

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2. Fermi Velocity Dependent Critical Current in Ballistic Bilayer Graphene Josephson Junctions

   https://doi.org/10.1021/acsnanoscienceau.4c00080  

   Sharma, Amis; Chen, Chun-Chia; McCourt, Jordan; Kim, Mingi; Watanabe, Kenji; Taniguchi, Takashi; Rokhinson, Leonid; Finkelstein, Gleb; Borzenets, Ivan (April 2025, ACS Nanoscience Au)

   We perform transport measurements on proximitized, ballistic, bilayer graphene Josephson junctions (BGJJs) in the intermediate-to-long junction regime (L > ξ). We measure the device’s differential resistance as a function of bias current and gate voltage for a range of different temperatures. The extracted critical current IC follows an exponential trend with temperature: exp(−kBT/δE). Here δE = ℏνF/2πL: an expected trend for intermediate-to-long junctions. From δE, we determine the Fermi velocity of the bilayer graphene, which is found to increase with gate voltage. Simultaneously, we show the carrier density dependence of δE, which is attributed to the quadratic dispersion of bilayer graphene. This is in contrast to single layer graphene Josephson junctions, where δE and the Fermi velocity are independent of the carrier density. The carrier density dependence in BGJJs allows for additional tuning parameters in graphene-based Josephson junction devices. 

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3. Study of graphene p-n junctions formed by the electrostatic modification of the SiO2 substrate

   https://doi.org/10.1038/s41598-024-61683-2  

   Nanayakkara, Tharanga R; Wijewardena, U Kushan; Kriisa, Annika; Mani, Ramesh G (May 2024, Scientific Reports)

   Abstract We study the transport properties of mm-scale CVD graphene p-n junctions, which are formed in a single gated graphene field effect transistor configuration. Here, an electrical-stressing-voltage technique served to modify the electrostatic potential in the SiO₂/Si substrate and create the p-n junction. We examine the transport characteristics about the Dirac points that are localized in the perturbed and unperturbed regions in the graphene channel and note the quantitative differences in the Hall effect between the perturbed and unperturbed regions. The results also show that the longitudinal resistance is highly sensitive to the external magnetic field when the Hall bar device operates as a p-n junction. 

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4. Chiral edge state control of thermoelectric effects

   https://doi.org/10.1126/sciadv.ady9006  

   Huynh, William; Liu, Boliang; Munyan, Simon; Ahadi, Sina; Stemmer, Susanne (September 2025, Science Advances)

   Thermoelectric responses in two-dimensional electron gases subjected to magnetic fields have the potential to provide unique information about quasiparticle statistics. In this study, we show that chiral edge states play a key role in thermoelectric Hall bar measurements by completely controlling the direction of the internal thermal gradient. To this end, we perform measurements of the magnetothermoelectric responses of cadmium arsenide quantum wells. The magnetothermoelectric responses in the quantum Hall regime agree with theoretical predictions if one considers the role of chiral edge states, which flow in opposite directions on either side of the Hall bar and establish an internal temperature gradient that is perpendicular to the externally applied thermal gradient. We show that the results are self-consistent within this picture under different measurement conditions. We discuss potential applications of the findings, such as in nanoscale control of local temperature gradients and thermoelectric effects along with the characterization of other topological systems with chiral edges states. 

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5. Creation of chiral interface channels for quantized transport in magnetic topological insulator multilayer heterostructures

   https://doi.org/10.1038/s41467-023-36488-y  

   Zhao, Yi-Fan; Zhang, Ruoxi; Cai, Jiaqi; Zhuo, Deyi; Zhou, Ling-Jie; Yan, Zi-Jie; Chan, Moses H.; Xu, Xiaodong; Chang, Cui-Zu (December 2023, Nature Communications)

   Abstract One-dimensional chiral interface channels can be created at the boundary of two quantum anomalous Hall (QAH) insulators with different Chern numbers. Such a QAH junction may function as a chiral edge current distributer at zero magnetic field, but its realization remains challenging. Here, by employing an in-situ mechanical mask, we use molecular beam epitaxy to synthesize QAH insulator junctions, in which two QAH insulators with different Chern numbers are connected along a one-dimensional junction. For the junction between Chern numbers of 1 and −1, we observe quantized transport and demonstrate the appearance of the two parallel propagating chiral interface channels along the magnetic domain wall at zero magnetic field. For the junction between Chern numbers of 1 and 2, our quantized transport shows that a single chiral interface channel appears at the interface. Our work lays the foundation for the development of QAH insulator-based electronic and spintronic devices and topological chiral networks. 

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