CMSA Strongly Correlated Quantum Materials and High-Temperature Superconductors Series: Universality vs materials-dependence in cuprates: New signatures of the pseudogap phase of cuprate superconductors


View Calendar
October 15, 2020 10:30 am - 12:00 pm
via Zoom Video Conferencing

Louis Taillefer - University of Sherbrooke

The pseudogap phase of cuprate superconductors is arguably the most enigmatic phase of quantum matter. We aim to shed new light on this phase by investigating the non- superconducting ground state of several cuprate materials at low temperature across a wide doping range, suppressing superconductivity with a magnetic field. Hall effect measurements across the pseudogap critical doping p* reveal a sharp drop in carrier density n from n = 1 + p above p* to n = p below p*, signaling a major transformation of the Fermi surface. Angle-dependent magneto-resistance (ADMR) directly reveals a change in Fermi surface topology across p*. From specific heat measurements, we observe the classic thermodynamic signatures of quantum criticality: the electronic specific heat C el shows a sharp peak at p*, where it varies in temperature as C el ~ – T logT. At p* and just above, the electrical resistivity is linear in T at low T, with an inelastic scattering rate that obeys the Planckian limit. Finally, the pseudogap phase is found to have a large negative thermal Hall conductivity, which extends to zero doping. We show that the pseudogap phase makes phonons become chiral.
Understanding the mechanisms responsible for these various new signatures will help elucidate the nature of the pseudogap phase.