Vendredi 23 janvier 2015 à 14h15
Grand auditoire, Ecole de Physique

Bosonic Theory of Superconductivity

Assa Auerbach, Technion

Historically, two paradigms competed to explain superconductivity (i) Bose Einstein Condensation (BEC) of weakly interacting Charge 2e pairs (Schafroth), and (ii) Pairing instability of the Fermi liquid (BCS). BCS theory was the unquestionable winner until the late 80's. BCS approximations however, have suffered major setbacks in the advent of high temperature, short coherence length superconductors, such as cuprates, pnictides, and granular superconducting films. A third paradigm has offered itself for understanding some properties of unconventional superconductors: Strongly Interacting Lattice Bosons (LB). LB behave less like in BEC's or or BCS theory, but (strangely) more like localized quantum spins. Their static correlations are very well understood by theories of quantum antiferromagnets. Their dynamics have only recently been explored. Near commensurate fillings, recent cold atom and thin films experiments have discovered the condensed matter version of the Higgs/ Amplitude mode. Conductivity of Lattice Bosons exhibit strange metallic properties, such as linear in temperature resistivity. LB also exhibit interesting vortex dynamics and Hall conductivity sign reversals.