Research Interests

My research is currently focused on quantum transport and optoelectronic measurements in low dimensional materials and combination of 2D materials stacked together as van der Waals heterostructures. Graphene is a material of choice in this field.

General Reading:

Quantum Hall effect in graphene heterostructures

The quantum Hall effect represents an experimental manifestation of quantum mechanics and topology in condensed matter systems. It provides a powerful experimental tool for studying the interactions between electrons in two-dimensional systems exposed to high magnetic fields. I am interested in investigating the quantum Hall effect in a variety of systems and harnessing quantum Hall edges to create novel electronic states. For example, graphene superlattices exhibit a complex fractal spectrum, that can be viewed as a collection of Landau levels arising from quantisation of Brown-Zak minibands recurring at rational (p/q) fractions of the magnetic flux per superlattice unit cell. Another example is the quantum Hall effect observed in thin graphitic films. We observed evidences of phase transitions and surface-mediated transport.

Recent articles on the topic:
  1. Robust 1D Proximity Superconductivity along Graphene Domain Walls In the Quantum Hall Regime, (2023). [arXiv:2402.14451]
    @unpublished{barrier2024nature,
      author = {Barrier, Julien and Xin, Na and Kim, Minsoo and Krishna Kumar, Roshan and Kumaravadivel, Piranavan and Hague, Lee and Nguyen, Ekaterina and Berdyugin, Alexey I and Moulsdale, Christian and Enaldiev, Vladimir V and Prance, Jonathan R and Koppens, Frank H L and Gorbachev, Roman V and Watanabe, Kenji and Taniguchi, Takashi and Glazman, Leonid I and Grigorieva, Irina V and Fal'ko, Vladimir I and Geim, Andre K},
      title = {Robust 1D proximity superconductivity along graphene domain walls in
              the quantum Hall regime},
      year = {2023},
      arxiv = {2402.14451}
    }
    
  2. Long-Range Ballistic Transport of Brown-Zak Fermions in Graphene Superlattices, Nature Communications 11, 5756 (2020). [arXiv:2006.15040] [DOI] [PDF] [SI]
    @article{barriernatcomms2020,
      title = {Long-range ballistic transport of Brown-Zak fermions in graphene
               superlattices},
      author = {Barrier, Julien and Kumaravadivel, Piranavan and Krishna-Kumar, Roshan and Ponomarenko, Leonid A. and Xin, Na and Holwill, Matthew and Mullan, Ciaran and Kim, Minsoo and Gorbachev, Roman V. and Thompson, Michael D. and Prance, Jonathan R. and Taniguchi, Takashi and Watanabe, Kenji and Grigorieva, Irina V. and Novoselov, Kostya S. and Mishchenko, Artem and Fal'ko, Vladimir I. and Berdyugin, Alexey I. and Geim, Andre K.},
      journal = {Nature communications},
      volume = {11},
      pages = {5756},
      year = {2020},
      publisher = {Nature Publishing Group},
      doi = {10.1038/s41467-020-19604-0},
      arxiv = {2006.15040}
    }
    
  3. Electronic Phase Separation in Multilayer Rhombohedral Graphite, Nature 584, 210 (2020). [arXiv:1911.04565] [DOI]
    @article{shinature2020,
      title = {Electronic phase separation in multilayer rhombohedral graphite},
      author = {Shi, Yanmeng and Xu, Shuigang and Yang, Yaping and Slizovskiy, Sergey and Morozov, Sergei V. and Son, Seok-Kyun and Ozdemir, Servet and Mullan, Ciaran and Barrier, Julien and Yin, Jun and Berdyugin, Alexei I. and Piot, Benjamin A. and Taniguchi, Takashi and Watanabe, Kenji and Fal'ko, Vladimir I. and Novoselov, Kostya S. and Geim, Andre K. Geim and Mishchenko, Artem},
      journal = {Nature},
      volume = {584},
      pages = {210--214},
      year = {2020},
      publisher = {Nature Publishing Group},
      doi = {10.1038/s41586-020-2568-2},
      arxiv = {1911.04565}
    }
    

High temperature quantum transport

Dirac fermions have a linear dispersion relation: their energy is proportional to their momentum. This unique properties is present in graphene and topological insulators. Under high temperatures, the intrinsic behaviour of Dirac fermions can emerge in an electron-hole plasma of Dirac fermions. I have investigated the behaviour of the Dirac plasma under high magnetic fields, reporting magnetotransport in this quantum-critical regime. This direction could offer advances in other fields, such as magnetotransport in strange metals or Weyl metals. Another project was dedicated on magnetotransport in graphene superlattices, where Brown-Zak fermions were observed as longitudinal resistance maxima for fixed fields.

Recent articles on the topic:
  1. Giant Magnetoresistance of Dirac Plasma in High-Mobility Graphene, Nature 616, 270 (2023). [arXiv:2302.06863] [DOI]
    @article{xin2023nature,
      author = {Xin, Na and Lourembam, James and Kumaravadivel, Piran and Kazantsev, Alexander E and Wu, Zefei and Mullan, Ciaran and Barrier, Julien and Geim, Alexandra A and Grigorieva, Irina V and Mishchenko, Artem and Principi, Alessandro and Fal'ko, Vladimir I and Ponomarenko, Leonid A and Geim, Andre K and Berdyugin, Alexey I},
      title = {Giant magnetoresistance of Dirac plasma in high-mobility graphene},
      year = {2023},
      journal = {Nature},
      pages = {270--274},
      volume = {616},
      issue = {7956},
      arxiv = {2302.06863},
      doi = {10.1038/s41586-023-05807-0}
    }
    
  2. Long-Range Ballistic Transport of Brown-Zak Fermions in Graphene Superlattices, Nature Communications 11, 5756 (2020). [arXiv:2006.15040] [DOI] [PDF] [SI]
    @article{barriernatcomms2020,
      title = {Long-range ballistic transport of Brown-Zak fermions in graphene
               superlattices},
      author = {Barrier, Julien and Kumaravadivel, Piranavan and Krishna-Kumar, Roshan and Ponomarenko, Leonid A. and Xin, Na and Holwill, Matthew and Mullan, Ciaran and Kim, Minsoo and Gorbachev, Roman V. and Thompson, Michael D. and Prance, Jonathan R. and Taniguchi, Takashi and Watanabe, Kenji and Grigorieva, Irina V. and Novoselov, Kostya S. and Mishchenko, Artem and Fal'ko, Vladimir I. and Berdyugin, Alexey I. and Geim, Andre K.},
      journal = {Nature communications},
      volume = {11},
      pages = {5756},
      year = {2020},
      publisher = {Nature Publishing Group},
      doi = {10.1038/s41467-020-19604-0},
      arxiv = {2006.15040}
    }