Le boson de Higgs dans les supraconducteurs

par Grégory Setnikar

Projet de thèse en Physique de la Matière Condensée et du Rayonnement

Sous la direction de Matteo D'astuto et de Marie-Aude Méasson.

Thèses en préparation à l'Université Grenoble Alpes , dans le cadre de École doctorale physique , en partenariat avec Institut Néel (laboratoire) et de Matière Condensée, Matériaux et Fonctions (equipe de recherche) depuis le 03-10-2018 .


  • Résumé

    When a spontaneous breaking of a continuous symmetry takes place, for instance when crossing the normal to superconducting transition, collective excitations of the order parameter emerge: They are the phase modes and the massive amplitude Higgs mode. While the quest for the Higgs boson in particle physics has reached its goal and its prediction has been rewarded with the Nobel Prize, there is growing interest in the search for analogous excitation in quantum many body systems, notably in superconductors. Indeed, even if theoretically always here in any superconductors and even if presented as a textbook excitation, this ‘dark' mode (like the Higgs boson in particle physics) remains very elusive. In principle, it does not couple to any external probe. Our purpose is to identify this Higgs mode in compounds where such excitation has been claimed to be present and to search for new Higgs mode in new compounds, in order to provide some textbook examples. Research topic and facilities available: The compounds where a superconducting Higgs mode has been claimed to be present are the ones where superconductivity coexists with another type of electronic order, such as charge density wave. In these systems, like in NbSe2, the amplitude oscillations of the CDW order parameter (CDW mode) can be detected by Raman spectroscopy. When the system becomes superconductor, a new Raman peak emerges. It has been attributed to the Higgs mode. Still, this example is unique among all known compounds. The student will explore a new family of compounds. Our goal is to discuss the universality of the detection of such mode. The student will perform symmetry dependent electronic Raman scattering experiment at low temperature and under high pressure on a chosen family of superconductors. Possible collaboration and networking: We already have a close theoretical collaboration with Lara Benfatto (ISC/Roma) on this topic. Collaboration with samples' growers is also established. Networking: ANR project.

  • Titre traduit

    Higgs boson in Superconductors


  • Résumé

    When a spontaneous breaking of a continuous symmetry takes place, for instance when crossing the normal to superconducting transition, collective excitations of the order parameter emerge: They are the phase modes and the massive amplitude Higgs mode. While the quest for the Higgs boson in particle physics has reached its goal and its prediction has been rewarded with the Nobel Prize, there is growing interest in the search for analogous excitation in quantum many body systems, notably in superconductors. Indeed, even if theoretically always here in any superconductors and even if presented as a textbook excitation, this ‘dark' mode (like the Higgs boson in particle physics) remains very elusive. In principle, it does not couple to any external probe. Our purpose is to identify this Higgs mode in compounds where such excitation has been claimed to be present and to search for new Higgs mode in new compounds, in order to provide some textbook examples. Research topic and facilities available: The compounds where a superconducting Higgs mode has been claimed to be present are the ones where superconductivity coexists with another type of electronic order, such as charge density wave. In these systems, like in NbSe2, the amplitude oscillations of the CDW order parameter (CDW mode) can be detected by Raman spectroscopy. When the system becomes superconductor, a new Raman peak emerges. It has been attributed to the Higgs mode. Still, this example is unique among all known compounds. The student will explore a new family of compounds. Our goal is to discuss the universality of the detection of such mode. The student will perform symmetry dependent electronic Raman scattering experiment at low temperature and under high pressure on a chosen family of superconductors. Possible collaboration and networking: We already have a close theoretical collaboration with Lara Benfatto (ISC/Roma) on this topic. Collaboration with samples' growers is also established. Networking: ANR project.