Low-dimensional (super)conductors at low temperature or high magnetic field are a fantastic playground for experimentalists. Our research activities aim at unveiling new quantum phenomena related to 2d superconductivity, quantum localization, and quantum Hall effect. We are currently focusing on:
- Control of quantum coherence in the quantum Hall effect in graphene
- Strongly disordered superconductors and the Cooper-pair insulator
- Topological Josephson junctions
- Ionic liquid gating
Our fields of expertise cover state-of-the-art nanofabrication, quantum transport of mesoscopic devices, and low-temperature/high field STM spectroscopy.
Electron interferometry with quantum Hall (QH) edge channels in semiconductor heterostructures can probe and harness the exchange statistics of anyonic excitations. In this work we show that high-mobility monolayer graphene constitutes an alternative material system, not affected by charging effects, for performing Fabry–Pérot QH interferometry in the integer QH regime.
C. Déprez, L. Veyrat, H. Vignaud, G. Nayak, K. Watanabe, T. Taniguchi, F. Gay, H. Sellier and B. Sacépé, Nature Nanotechnology 16, 555 (2021)
This Review Article summarizes recent progress in understanding of the various pathways that lead to the destruction of superconductivity by the interplay of disorder, localization and interactions, including experiments in low dimensional materials and application in superconducting quantum devices.
B. Sacépé, M. Feigel’man, T. Klapwijk, Nature Physics 7, 734 (2020)
We unveiled a new interaction-induced topological phase in the zeroth Landau level of graphene. This phase is insulating in the bulk and exhibits a pair of spin-filtered, helical edge channels. It emerges under moderate perpendicular magnetic field when graphene is placed in proximity to a high-k dielectric substrate. In this work we demonstrated a remarkably robust quantum spin Hall effect that withstands up to 110 K over micron-long distances which opens a new avenue for spintronics and topological superconductivity.
The search for experimental evidence of Majorana modes is an area of intense research in condensed matter and quantum physics and uncovering clear evidence is complicated. We investigate the impact of Joule heating which can influence the analysis of experimental features related to Majorana bound states in topological Josephson junctions.
K. Le Calvez, L. Veyrat, F. Gay, P. Plaindoux, C. Winkelmann, H. Courtois, B. Sacépé, Communications Physics, 2:4 (2019)
Transport measurements performed on MoGe superconducting nanowires reveal a quantitative agreement with quantum critical behaviour driven by a pair-breaking mechanism.
Hyunjeong Kim, Frédéric Gay, Adrian Del Maestro, Benjamin Sacépé, Andrey Rogachev. Nature Physics 14, 912-917 (2018)
High mobility graphene van der Waals heterostructures equipped with split-gate electrodes enable to control the transmission of integer and fractional quantum Hall edge channels in a gate tunable fashion, demonstrating Quantum Point Contact operation in the quantum Hall regime of graphene.
Anna Jordan, Frédéric Gay, Kenji Watanabe, Takashi Taniguchi, Zheng Han, Vincent Bouchiat, Hermann Sellier, Benjamin Sacépé, Nature Communications 8:14983 (2017)