Accueil > Agenda Scientifique

Les événements de novembre 2017

séminaire

<p>séminaire</p>
  • Séminaire des doctorants

    • Jeudi 16 novembre 11:00-12:00 - Rosa Lopez - nstitute for Cross-Disciplinary Physics and Complex Systems IFISC (UIB-CSIC), Palma de Mallorca, Spain

      A Chiral Maxwell Demon

      Résumé : Maxwells demon is characterized by a hypothetical intelligence capable of sorting hot (fast) and cold (slow) atoms to left and right sub-cavities in a box by simply matchingly inserting and removing an impenetrable wall. This concept was suggested by J.C. Maxwell to highlight that thermodynamics is a macroscopic theory. Under ideal conditions, inserting and removing the wall would not require work and the apparent contradiction with the second law the entropy in the box would be reduced and after the sorting process, work could be extracted from the temperature difference between the sub-cavities has been a source of much debate ever since1. It is now generally believed that this paradox is overcome by the Landauer principle : Deleting the data required for the processing in the demons mind would at least generate entropy S = kBln2 or dissipate heat of at least Q = kBTln2 per bit of information, yielding a net production of entropy.
      The demon measures on the system and conditioned on the measurement result it decides its action which is formally nothing but a closed-loop feed-back control scheme. Here, we replace the two sub-cavities of the box by the magnetic field polarity that determines the chirality of the conducting channels. The chiral conductors are coupled to a quasilocalized level state. Depeneding on its occupation dynamics a nearby quantum point contact (QPC) choose one or other field polarity. In this manner the tunneling rates to the conductors are modified depending on the quasibound state occupation.In this work we will address the entropy production, power production, and efficiency when a magnetic feedback is considered.

      Lieu : salle 208a, aîle sud LPS, bât 510

      Article

  • Séminaire des doctorants

    • Jeudi 30 novembre 11:00-12:30 - David Carpentier - ENS Lyon

      The Chiral Anomaly and Ballistic Transport of Weyl Fermions

      Résumé : The chiral anomaly is a unique property of massless relativistic particles in three dimensions. While the chiral nature of particles was expected to be a conserved property, the breaking of this symmetry was a bizarre property of the associated field theory. The recent focus on materials in which low energy electrons behave as massless relativistic Weyl particles has opened the possibility to experimentally access consequences on transport of this field theory property. Indeed, an anomalous contribution to the conductance in the presence of a magnetic field was associated to the presence of the chiral anomaly. In this talk, I will focus on the different regime of ballistic transport of Weyl fermions in small mesoscopic conductors.
      I will show how the anomalous transport can be traced back to the presence of anomalous Landau Levels in such a junction, and to the chiral anomaly. I will finally comment on the relation between diffusive and ballistic regimes.

      Lieu : salle 208a, aîle sud LPS, bât 510

      Article

Ajouter un événement