Accueil > Agenda Scientifique

14 février 2019: 2 événements

séminaire

  • 3D quantum Hall effects in Dirac loops

    Jeudi 14 février 11:00-12:00 - Bruno Uchoa - University of Oklahoma

    3D quantum Hall effects in Dirac loops

    Résumé : Nodal-line semimetals describe a class of 3D systems where the low energy bands have Dirac quasiparticles along a closed line in momentum space (Dirac loop) rather than a discrete set of Dirac points [1]. One conceptually interesting family of lattice models that describes this physics is the family of the hyperhoneycomb lattices, which form 3D structures of crossed 1D chains where all sites have the same planar trigonal connectivity of graphene. In this talk, I will show that Coulomb interactions could drive the system to show an anomalous quantum Hall effect (AQHE) [2], with current loops that produce zero net flux in the 3D unit cell. I will show that in the AQH state, because of lack of inversion symmetry, the Haldane mass has nodes along the nodal line, giving rise to pairs of Weyl points connected by Fermi arcs. I will discuss the anomalous Hall conductivity of this system and the connections with strain field deformations encoded in the elastic Hall viscosity [3].
    [1] K. Mullen, B. Uchoa, D. Glatzhofer, Phys. Rev. Lett. 115, 026403 (2015).
    [2] S. W. Kim, K. Seo, B. Uchoa, Phys. Rev. B 97, 201101(R) (2018).
    [3] S. W. Kim, B. Uchoa, arXiv:1901.00574 (2019).

    Lieu : salle 315, aîle sud LPS, bât 510

    En savoir plus : 3D quantum Hall effects in Dirac loops
  • New insight into the pseudogap phase of cuprate superconductors thanks to transport measurements

    Jeudi 14 février 14:00-15:00 - Anaelle Legros - Service de Physique de l’Etat Condensé, CEA - Université de Sherbrooke, Canada

    New insight into the pseudogap phase of cuprate superconductors thanks to transport measurements

    Résumé : Cuprates, discovered more than thirty years ago, are peculiar superconductors that posess the highest critical temperatures known nowadays and display a complex temperature—doping phase diagram. One of the many phases in this diagram is the pseudogap phase, characterized by a partial drop in the density of states and whose nature remains unclear to date. Understanding the origin of the pseudogap in cuprate superconductors is essential to elucidate the cause of high critical temperatures in these materials. A way to investigate this peculiar state is to look for signatures of a phase transition in doping, at very low temperatures (in the T → 0 limit). In this presentation, we will show how transport measurements can be used to probe the critical doping p* where the pseudogap phase ends at T = 0. I will reveal some recent information provided by these measurements during my PhD. In addition, I will also present new results regarding the crystal growth of the mercury-based cuprate HgBa2CuO4+δ, a model cuprate synthesized only in a few research groups.

    Lieu : LPS, bât 510, Moyen Amphi

    En savoir plus : New insight into the pseudogap phase of cuprate superconductors thanks to transport measurements