{"id":583,"date":"2018-07-10T12:13:26","date_gmt":"2018-07-10T10:13:26","guid":{"rendered":"https:\/\/sacepe-quest.neel.cnrs.fr\/?page_id=583"},"modified":"2025-01-23T16:59:10","modified_gmt":"2025-01-23T15:59:10","slug":"highlights","status":"publish","type":"page","link":"https:\/\/sacepe-quest.neel.cnrs.fr\/index.php\/highlights\/","title":{"rendered":"Highlights"},"content":{"rendered":"

First-order quantum breakdown of superconductivity in an amorphous superconductor<\/a><\/h4>\n

\"\"We discovered that highly disordered superconductors, such as indium oxide films, undergo abrupt first-order quantum phase transitions, challenging traditional theories that assume gradual transitions. Our findings, which reveal a sharp drop in superfluid stiffness at a critical disorder level, have significant implications for quantum circuits that use disordered superconductors as superinductors. <\/p>\n

T. Charpentier, D. Perconte, S. L\u00e9ger, K. Amin, F. Blondelle, F. Gay, O. Buisson, Lev I., A. Khvalyuk, I. Poboiko, M. Feigel\u2019man, N. Roch, B. Sac\u00e9p\u00e9 Nature Physics (2025)<\/a><\/p>\n

Some news outlets: Quantum Insider<\/a>, Interesting Engineering<\/a>, Phys.org<\/a>, Cosmos<\/a><\/p>\n

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 <\/h4>\n

Evidence for correlated electron pairs and triplets in quantum Hall interferometers<\/a><\/h4>\n

\"\"This study we have evidenced unusual electron pairing and tripling phenomena without attractive interactions in graphene quantum Hall Fabry\u2013P\u00e9rot interferometers (QH FPIs). At a bulk filling factor of \u03bd = 2, electron pairing occurs  while at \u03bd = 3, electron tripling emerges, characterized by a fractional Aharonov\u2013Bohm flux period of h\/2e and h\/3e, respectively. Using plunger-gate spectroscopy, we show that charge transport in this pairing and tripling regime is correlated across two and three edge channels.<\/p>\n

W. Yang, D. Perconte, C. D\u00e9prez, K. Watanabe, T. Taniguchi, S. Dumont, E. Wagner, F. Gay, I. Safi, H. Sellier, B. Sac\u00e9p\u00e9 Nature Communications 15:10064 (2024)<\/a><\/p>\n

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 <\/h4>\n

Evidence for chiral supercurrent in quantum Hall Josephson junctions<\/a><\/h4>\n

\"\"In this work we have tackled the complex challenge of associating two emblematic quantum phenomena of condensed matter: the quantum Hall effect and superconductivity. We demonstrated the existence of a chiral Josephson supercurrent<\/em> with unprecedented properties flowing between two superconducting electrodes, connected by a graphene nanoribbon in the quantum Hall regime. This supercurrent is transported along the quantum Hall edge channels of the graphene, forming a chiral loop whose rotation direction depends on the sign of the magnetic field.<\/p>\n

H. Vignaud, D. Perconte, W. Yang, B. Kousar, E. Wagner, F. Gay, K. Watanabe, T. Taniguchi, H. Courtois, Z. han, H. Sellier, B. Sac\u00e9p\u00e9, Nature 624, 545 (2023)<\/a><\/strong><\/p>\n

 <\/p>\n

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Absence of edge reconstruction for quantum Hall edge channels in graphene devices<\/a><\/h4>\n

\"\"This study report on the first scanning tunneling spectroscopy of quantum Hall edge channels in graphene under a perpendicular magnetic field. Our work reveals that these edge channels are confined to a few magnetic lengths at crystal edges, confirming them as ideal 1D chiral channels without  electrostatic reconstruction. The findings carry implications for electron and heat transport experiments in graphene and other 2D crystalline materials.<\/p>\n

A. Coissard, A. G. Grushin<\/span>, C. Repellin<\/span>, L.Veyrat<\/span>, K. Watanabe<\/span>, T. Taniguchi<\/span>, F. Gay<\/span>, H. Courtois<\/span>, H. Sellier<\/span>, B. Sac\u00e9p\u00e9, <\/span><\/span><\/span>Science Advances <\/span>9, <\/span>eadf7220<\/span>(2023)<\/span><\/strong><\/a><\/p>\n

 <\/p>\n

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Imaging tunable quantum Hall broken-symmetry orders in graphene<\/a><\/h4>\n

\"\"When electrons populate a flat band their kinetic energy becomes negligible, forcing them to organize in exotic many-body states to minimize their Coulomb energy. The zeroth Landau level of graphene under a magnetic field is a particularly interesting strongly interacting flat band because interelectron interactions are predicted to induce a rich variety of broken-symmetry states with distinct topological and lattice-scale orders, which we evidence in this work.<\/p>\n

A. Coissard, D. Wander, H. Vignaud, A. G. Grushin, C. Repellin, K. Watanabe, T. Taniguchi, F. Gay, C. B. Winkelmann, H. Courtois, H. Sellier, B. Sac\u00e9p\u00e9, Nature 605, 51 (2022)<\/a><\/strong><\/p>\n

 <\/p>\n

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A tunable Fabry-P\u00e9rot quantum Hall interferometer in graphene<\/a><\/h4>\n

\"\"<\/p>\n

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\u2013P\u00e9rot QH interferometry in the integer QH regime.<\/p>\n

C. D\u00e9prez, L. Veyrat, H. Vignaud, G. Nayak, K. Watanabe, T. Taniguchi, F. Gay, H. Sellier and B. Sac\u00e9p\u00e9, Nature Nanotechnology 16, 555 (2021)<\/strong><\/a><\/p>\n

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Review Article: Quantum breakdown of superconductivity in low-dimensional materials<\/a><\/h4>\n

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. <\/p>\n

B. Sac\u00e9p\u00e9, M. Feigel’man, T. Klapwijk, Nature Physics 7, 734 (2020)<\/a><\/strong><\/p>\n

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Helical quantum Hall phase in graphene on SrTiO3<\/strong><\/a><\/h4>\n

\"\"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.<\/p>\n

L. Veyrat, C. Deprez, A. Coissard, X. Li, F. Gay, K. Watanabe, T. Taniguchi, Vitto Han, B. Piot, H. Sellier, B. Sac\u00e9p\u00e9, Science 367, 781 (2020)<\/a><\/strong><\/p>\n

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When Joule poisons Majorana in topological Josephson junctions<\/strong>\"\"<\/a><\/h4>\n

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.<\/p>\n

K. Le Calvez, L. Veyrat, F. Gay, P. Plaindoux, C. Winkelmann, H. Courtois, B. Sac\u00e9p\u00e9, Communications Physics<\/strong> 2:4 (2019)<\/a><\/p>\n

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Low-temperature anomaly in disordered superconductors near B<\/span>c<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/strong>2 as a vortex-glass property<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/strong><\/a>\"\"<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/h4>\n
Strongly disor<\/span>dered super<\/span>c<\/span>onductors in a magnetic field e<\/span>xhibit many char<\/span>acteristic properties of type-II super<\/span>conductivit<\/span>y<\/span>\u2014<\/span>ex<\/span>cept at lo<\/span>w temper<\/span>atur<\/span>es, where an anomalous linear t<\/span>emper<\/span>ature <\/span>dependenc<\/span>e of the r<\/span>esistiv<\/span>e critical field B<\/span>c2<\/span> is routinely <\/span>observ<\/span>ed. Here we<\/span><\/span> r<\/span>eport sy<\/span>stematic measur<\/span>ements of the critical magnetic field and current on amorphous indium o<\/span>xide films which <\/span>show that the B<\/span>c2 <\/span>anomaly is acc<\/span>ompanied by mean-<\/span>field-lik<\/span>e scaling of <\/span>the critical current. Based on a c<\/span>omprehensiv<\/span>e theoretical study w<\/span>e demonstrate that these observ<\/span>ations are a c<\/span>onsequenc<\/span>e of the <\/span>v<\/span>ortex<\/span>-glass gr<\/span>ound state and its thermal fluctuations.<\/span><\/div>\n
 <\/div>\n
 B. Sac\u00e9p\u00e9, J. Seidemann, F. Gay, K. Davenport, A. Rogachev, M. Ovadia, K. Michaeli, M. V. Feigel’man Nature Physics<\/strong><\/em> 15, 48-53 (2019)<\/a> <\/div>\n
 See also CNRS press release<\/em> : http:\/\/www.cnrs.fr\/inp\/spip.php?article6274<\/a><\/div>\n
 <\/div>\n
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Pair-breaking quantum phase transition in superconducting nanowires<\/strong>\"\"<\/a><\/h4>\n

Transport measurements performed on MoGe superconducting nanowires reveal a quantitative agreement with quantum critical behaviour driven by a pair-breaking mechanism.<\/p>\n

Hyunjeong Kim, Fr\u00e9d\u00e9ric Gay, Adrian Del Maestro, Benjamin Sac\u00e9p\u00e9, Andrey Rogachev. Nature Physics<\/strong><\/i> (2018)<\/span><\/a><\/p>\n

 <\/p>\n

 <\/p>\n

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Pinching off electron edge-channels in graphene<\/strong>\"\"<\/a><\/h4>\n

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.<\/p>\n

Anna Jordan, <\/span>Fr\u00e9d\u00e9ric Gay, <\/span>Kenji Watanabe, <\/span>Takashi Taniguchi, <\/span>Zheng Han, Vincent Bouchiat, Hermann Sellier, <\/span>Benjamin Sac\u00e9p\u00e9, Nature Communications<\/em><\/strong> 8:14983 (2017)<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

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