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Quantum nanostructures and topological matter

Research team at LNCMI Toulouse
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Nanoscience and nanophysics are fascinating research areas at the frontier between fundamental physics and material science. Exploring the physical, optical, and electronic properties of various nano-objects and nanostructures made of novel materials is an essential fundamental step before their integration in tomorrow’s miniaturized electronic devices.

The application of a strong magnetic field together with the use of very low temperatures constitutes an extreme experimental environment favorable to the discovery of the fundamental electronic properties of nanostructures. By acting on the charge and the spin of the electrons responsible for the flow of electrical current in the nanostructures, the magnetic field helps to reveal some of their electronic properties, through the observation of Hall effect or quantum oscillations for example. A strong magnetic field can also drive the studied nanostructures in new quantum states of matter, such as the quantum Hall effect.

At the interface between condensed-matter physics, semiconductor physics, and quantum physics, our research group has specialized in transport experiments on nanostructures under very high magnetic fields. We exploit the pulsed magnetic fields generated at the Toulouse site of the laboratory, and, therefore, seek for effects which appear in the 40-70T range.

The fabrication, manipulation, electrical connection, and finally the characterization of nanostructures under pulsed magnetic fields are experimental challenges that our team is taking up every day. The systems under study are, among others, carbon nanotubes, graphene and graphene nano-ribbons, thin graphite, two-dimensional electron gas at the interface of complex oxides, monolayers of transition metal dichalcogenides, as well as various semi-conducting and semi-metallic nanostructures.

As part of our activities, we welcome researchers working on this research topic from all around the world for performing experiments using our equipements and knowledge.

We are open to students and post-docs willing to join our research group all along the year. Please contact us.

Experiments on planar Hall effect in PtBi2 with Dr. Qu Jiang and Ankit Kumar

In May 2025, we welcomed Qu Jiang and Ankit Kumar, respectively post-doctoral reasearcher and PhD...
Read More

Experiments on graphite at 70T with Dr. Bruno Camargo

In February 2025, we welcomed Bruno Camargo, a researcher at the Institute of Experimental Physics...
Read More
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Research Thematics

2D materials

Investigated systems:

  • Pristine and functionalized graphene (collab. O. Makarovskiy, University of Nottingham, UK)

  • Transition metal dichalcogenide (TMDC) monolayers and thin flakes

  • Complex oxide interfaces (collab. Ariando, NUS Singapore)

 

Topological Matter

Topology in condensed matter is a novel intrinsic characteritics of a material system which greatly influences its physical properties. The main characteristics of non-trivial topological systems is the existence of metallic interface states at their interface with systems of other topological class (typically, trivial systems). Depending on the dimensionality of the system, there can be 2D surface states (3D topological insulators, Weyl semimetals) or 1D edge states (Quantum Hall effect, Quantum Spin Hall effect, Quantum anomalous Hall effect). We investigate the intrinsic properties of topological system using quantum transport in very high magnetic fields (up to 70T) and at cryogenic temperatures (down to 1.5K).

Investigated systems:

  • 3D topological insulator: BiSb, BiSbTe (collab. C. Durand & S. Plissard, LAAS)
  • Magnetic 3D topological insulators: MnBi2Te4, EuSn2As2 (collab. J. Dufouleur & R. Giraud, IFW-Dresden & SPINTECH)
  • Weyl & nodal line semimetals: PtBi2 (collab. J. Dufouleur, IFW-Dresden)
  • 2D topological insulator: InAs/GaSb quantum wells (collab. B. Jouault, L2C)
  • Non-hermitian topology in graphene (collab. J. Dufouleur, IFW-Dresden)

 

Superconducting nanostructures

Superconductivity is a state of matter characterized by a macroscopically coherent quantum state that enables electricity to flow without dissipation. It occurs in 3D bulk materials but also in 2D materials (graphene, TMDs, …) or at metallic interfaces in complex oxides (LAO/STO) and in 1D nanowires. The superconducting state can also be greatly influenced by the nanostructure of the material, especially in terms of vortex pinning which define its critical current in a magnetic field. We study the properties of superconductors with reduced dimensionality: exfoliated heterostructures, nanostructures, thin films etc… using electrical transport measurements (nA to A, nV to V) in very high magnetic fields (up to 70T, angular dependence, gate-tunable) and at cryogenic temperatures (pumped 3He, down to 0.5 K).

Investigated systems:

  • Weyl semimetals: PtBi2 (collab. J. Dufouleur, IFW-Dresden)
  • Nickelates ultra-thin films (collab. Ariando, NUS Singapore)
  • REBCO superconducting tapes with nm-sized artificial pinning centers
  • Complex Oxides

 

Experimental techniques

Magneto-transport under pulsed magnetic field

Our team is expert in studying electronic transport in nanostructures under pulsed magnetic field. With over two decades of experience, we can safely handle fragile, electrostatic-sensitive nanodevices in the extreme environement required for the production of high, pulsed magnetic field, where 24kV is suddenly applied to the coil with several tens of thousands amps running in it. Our measurement inserts are designed for the following experimental conditions:

  • 60T coil. Temperature range: 1.5K – 300K. In-situ rotation. The sample can be rotated by more than 90° with respect to the magnetic field direction, allowing investigations from perpendicular to in-plane magnetic field for 2D electron gas, and from perpendicular to along-the-axis field for 1D conductors.
  • 60T coil. Temperature range: 350mK – 300K. No rotation.
  • 70T coil. Temperature range: 1.5K – 300K. No rotation. 

 

Nanofabrication

Our laboratory is equipped for the fabrication of nanostructures. Very often, we aim at contacting our nanostructures with microfabricated electrodes, for the purpose of conducting transport experiments.

We also co-founded the exfolab platform, hosted at LPCNO, where van der Waals heterostructures can be made by stacking monolayers or thin flakes of van der Waals materials.

Publications

All publications of the team

 2024

  • Non-Hermitian topology in a multi-terminal quantum Hall device
    Kyrylo Ochkan, Raghav Chaturvedi, Viktor Könye, Louis Veyrat, Romain Giraud, Dominique Mailly, Antonella Cavanna, Ulf Gennser, Ewelina M Hankiewicz, Bernd Büchner, Jeroen van den Brink, Joseph Dufouleur, and Ion Cosma Fulga
    Nature Physics volume 20, pages 395–401 (2024)
  • Dissipationless transport signature of topological nodal lines (arXiv)
    Arthur Veyrat, Klaus Koepernik, Louis Veyrat, Grigory Shipunov, Saicharan Aswartham, Jiang Qu, Ankit Kumar, Michele Ceccardi, Federico Caglieris, Nicolás Pérez Rodríguez, Romain Giraud, Bernd Büchner, Jeroen van den Brink, Carmine Ortix, and Joseph Dufouleur
    arXiv:2410.02353 (2024), to appear in Nature Communication
  • Non-Hermitian topology in the quantum Hall effect of graphene (arXiv)
    Burak Özer, Kyrylo Ochkan, Raghav Chaturvedi, Evgenii Maltsev, Viktor Könye, Romain Giraud, Arthur Veyrat, Ewelina M Hankiewicz, Kenji Watanabe, Takashi Taniguchi, Bernd Büchner, Jeroen van den Brink, Ion Cosma Fulga, Joseph Dufouleur, and Louis Veyrat
    arXiv:2410.14329 (2024)

2023

2022

2021

2020

2019

2018

2017

2016

2015

  • Band Bending Inversion in Bi2Se3 Nanostructures (arXiv)
    Louis Veyrat, Fabrice Iacovella, Joseph Dufouleur, Christian Nowka, Hannes Funke, Ming Yang, Walter Escoffier, Michel Goiran, Barbara Eichler, Oliver G. Schmidt, Bernd Büchner, Silke Hampel, and Romain Giraud
    Nano Letters 15, 7503–7507

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2006

2005

2003

    Former members of the group

    PhD students
    • Haoliang Shen
      Dual Ph.D. degree with Nanjing University, China, 2015
    Post-docs
    • Rubi Km
      Researcher at the National High Magnetic Field Laboratory, Los Alamos National Laboratory, USA
    • Bruno Camargo
      Researcher at the Institute of Experimental Physics, University of Warsaw, Poland
    • Amit Kumar