Domain, Specialties : Condensed matter physics
Keywords: Mescoscopic physics, quantum Hall effect, Coulomb blockade
Research Unit : SPEC / GQ
Summary
In reduced dimensionality, particles coined “anyons” can evade the familiar division between fermions and bosons with a fractional exchange phase between 0 and pi, with applications to topological quantum computation. Early on, quasiparticles of the Fractional Quantum Hall regime were identified as anyon candidates, and their fractional statistics was experimentally established in a few pioneer experiments in the early 2020s [1]. It has been suggested [2] that their existence extends way beyond this restrictive framework, and that they emerge for instance in bidimensional ballistic electron systems with strong Coulomb interactions, resulting in electron charge and statistics fractionalization.
The goal of this internship is to follow this novel approach with quantum circuit tools, combining quantum point contacts, single electron physics at high charging energies and ballistic edge channels of the Integer quantum Hall regime [3]. The student will learn a variety of techniques mastered in the team (ultrasensitive conductance and quantum shot noise measurements, quantum thermal transport, electron interferometry), in order to reveal the anyonic nature of the system’s excitations, and characterize their quantum coherence.
Collaborations are already established with C2N (Palaiseau) and LPENS (Paris) for nano-fabrication and experiments, and MPQ (Paris), U. Karlstad (Sweden), and KAIST (Daejeon, Korea) for theory.
[1] H. Bartolomei et al., Science 368, 173-177 (2020) ; J. Nakamura et al., Nat. Phys. 16, 931-936 (2020) ; P. Glidic et al., Phys. Rev. X 13, 011030 (2023) [2] T. Morel et al., Phys. Rev. B 105, 075433 (2022) [3] P. Roche et al., Phys. Rev. Lett. 136, 196301 (2026)
Full description
The division of particles into bosons and fermions is central to quantum mechanics. However, this distinction has been challenged since the 1980s. In reduced dimensions, particles known as “anyons” can acquire an exchange phase in the two-particle wavefunction that lies between 0 (bosons) and π (fermions) [1], unlike in three dimensions, where the phase is constrained to take one of these two values. The existence of anyons was established experimentally only recently (2020), in two pioneering experiments [2] performed in the fractional quantum Hall effect (FQHE) regime. However, the experimental conditions required for their observation—ultra-low temperatures, magnetic fields above 10 T, and high-mobility two-dimensional electron gases—are not particularly favorable to rapid progress or to a detailed understanding of these objects. Moreover, the FQH regime is sensitive to numerous experimental artefacts caused by disorder in the samples, making it difficult to observe universal behaviour associated with these anyons.
The aim of this internship is to engineer and study anyons using a radically different approach, inspired by quantum circuits, based on deliberately introduced interactions that can be robustly controlled, outside the exotic regimes in which these particles usually emerge. This approach builds on two recent theoretical proposals [3], which suggest combining, in a 2D electron gas (based on semiconductor heterostructures or graphene), integer quantum Hall (IQH) edge channels partitioned by quantum point contacts (QPCs), with Coulomb blockade in a micron-sized metallic island that is electrically interfaced with the electron gas. Taken individually, the edge channels are simply described by non-interacting physics. Interactions are introduced through Coulomb blockade, whose strength is controlled by the size of the island. In this context, these interactions cause the fractionalization of individual electrons injected by a QPC: these electrons cannot accumulate on the island without expelling fractional-charge plasmons into each channel emerging from the island, in order to satisfy charge conservation. The degree of fractionalization is therefore directly determined by the number of outgoing channels. The fractional statistics of these individual wave packets can then be revealed through a precise measurement of the shot noise of a QPC acting as a scatterer across one of these channels: the noise carries a quantitative signature of the fractional exchange phase.
The internship will be carried out within the Quantronics group, which has access to numerous dilution refrigerators—necessary to reach temperatures negligible compared with the relevant interaction energy scales—several of which are equipped with sufficiently high magnetic fields to reach the integer quantum Hall regime. The group also has leading expertise in quantum transport and noise measurements. Preliminary measurements have already demonstrated the feasibility of this approach: we have been able to characterize sufficiently small islands exhibiting an essentially perfect interface with a 2D electron gas provided by the C2N (Palaiseau). Such islands can also be fabricated in graphene, as we recently demonstrated [4], providing considerable flexibility in the choice of host material. Existing collaborations for nanofabrication include C2N, both for samples based on semiconductor heterostructures (D. Mailly) and for graphene-based samples (R. Ribeiro-Palau, M. Kapfer). In addition, an ongoing collaboration with the ENS Physics Laboratory (F. Parmentier) focuses on complementary measurements of quantum heat transport in strongly correlated electronic systems. The theoretical analysis will be conducted in collaboration with theorists from MPQ, Karlstad University, and KAIST in South Korea, who developed the theoretical proposals underpinning this project.
- [1] J. M. Leinaas and J. Myrheim, Nuovo Cim. B 37, 1 (1977)
- [2] H. Bartolomei et al., Science 368, 173 (2020), J. Nakamura et al., Nature Physics 16¸ 931 (2020)
- [3] J.-Y. M. Lee et al., Phys. Rev. Lett. 125 (19), 196802 (2020), T. Morel et al., Phys. Rev. B 105, 075433 (2022)
- [4] A. Zhang et al., arXiv:2601.05694 (2026), prochainement publié dans Physical Review Letters
Location
France
Internship conditions
- Internship duration: 6 months
- Level of study: Bac+5
- Training: Master 2
- Continuation in PhD thesis: Yes
- Application deadline: january 31st 2027
Experimental skills
The student should have a Master level background in quantum physics and a taste for quantitative theory/experiment confrontation. Prior experience with cryogenics, mesoscopic physics or nanofabrication is good but not mandatory: motivation is a key factor.
Language : English
Useful methods and technics to be acquired during the internship:
Quantum transport, dilution refrigeration, high resolution electrical measurements (conductance, low- and high-frequency noise), clean room fabrication based on semiconducting two-dimensional electron gases and graphene.
Computer languages and software:
Python, Mathematica
Links
Personal page: https://iramis.cea.fr/en/spec/gq/pisp/olivier-maillet/
Supervisor
Olivier MAILLET
Phone: 01 69 08 73 33
Email :
Head of the laboratory SPEC / GQ
Hugues Pothier
Phone: 01 69 08 75 13