STAGE Superconductivity and topological states in twisted bilayer

Date de mise à jour de l’offre

Centre for Nanoscience and Nanotechnology :

Le Centre de Nanosciences et de Nanotechnologies - C2N (CNRS/Université Paris-Saclay), a été créé le 1er juin 2016 du regroupement de deux laboratoires franciliens leaders dans leur domaine : le Laboratoire de photonique et de nanostructures (LPN) et l'Institut d'électronique fondamentale (IEF). En 2018, les équipes se sont installées dans un nouveau bâtiment au cœur du Campus Paris-Saclay. Le collège de direction du Centre de Nanosciences et de Nanotechnologies est composé du directeur, Giancarlo Faini, des quatre directeurs adjoints Laurent Vivien, Arnaud Bournel, Pierre-Yves Joubert et Jean-Christophe Harmand, ainsi que de la secrétaire générale Vanessa Tocut.

Description de la mission

The first measurements of superconductivity and correlated phases in twisted bilayer graphene (tBLG) brought a lot of attention to this new way to control the properties of matter: twisting layersin a van der Waals heterostructure. The superconducting state in tBLG or twisted van der Waals structures is believed to have its origin in the interplay between the moiré superlattice and the interlayer interactions, which leads to the formation of a flat band in the electronic band structure.
Controlling the twist angle between the layers allows playing with both of these parameters at the same time. As layers get more aligned, the moiré superlattice wavelength and the layer
hybridization increases. However, as the twolayers get more and more aligned, at angles >1.1°, the superconducting temperature decreases. A remarkable change of the critical
superconducting temperature from 1.7 K to 0.5 K was reported for angular variations of 1.05 and 1.16 degrees in the case of tBLG [Cao et al., Nature 2018]. Given this astonishing result, we might wonder what is so special in the socalled magic-angle, 1.1 degrees and if other
magic angles can be found where flat bands can be observed. Up to now it seems that twisted bilayer graphene is the ideal playground for most of the condensed matter phenomena, from superconductivity to anomalous quantum Hall effect and other correlated phases. However, the most challenging part of this research seems to lay in a reliable fabrication of homogeneous samples. In our laboratory we have developed a new technique to continuously control the angular alignment between layers [Ribeiro et al., Science 2018].
During this internship (with the possibility to be extended for a PhD thesis) we will use the layer alignment technique combined with low temperature measurements of electron transport to reveal the phase diagram of the superconducting state and other strongly correlated effect. This phase diagram will allow us to understand the origin of the superconducting state as well as what are the parameters increasing the critical superconducting temperature.

Profil recherché

Master 2 en Physique ou Nanophysique

Niveau de qualification requis

Bac + 4/5 et +
  • Employeur
    Centre for Nanoscience and Nanotechnology
  • Secteur d’activité de la structure
    Enseignement - Formation - Recherche
  • Effectif de la structure
    De 51 à 250 salariés
  • Site internet de la structure
    https://www.c2n.universite-paris-saclay.fr
  • Type de stage ou contrat
    Stage pour lycéens et étudiants en formation initiale
  • Date prévisionnelle de démarrage
  • Durée du stage ou contrat
    Plus de 4 mois et jusqu'à 6 mois
  • Le stage est-il rémunéré ?
    Oui
  • Niveau de qualification requis

    Bac + 4/5 et +
  • Lieu du stage
    10 boulevard Thomas Gobert
    91120 PALAISEAU
  • Accès et transports
    RER et bus