Dartmouth Events

Abstract: High-temperature superconductors have a rich phase diagram with many competing orders including anti- ferromagnetism and d-wave superconductivity. In this talk I will focus on the pseudogap phase of cuprate superconductors, which is characterized by the appearance of a normal-state gap in the fermionic spectrum in the absence of condensation. One possible interpretation of this phase is that of fluctuating Cooper pairs – pairs of electrons that bind together without forming a condensate. A strong piece of evidence for this viewpoint is the experimentally observed large value for the diamagnetic susceptibility. Also of great interest have been the recent results for the Hall and thermal Hall coefficients. I will outline the theoretical results for the diamagnetic susceptibility, electrical conductivity, and thermal conductivity for a specific fluctuation theory that includes the normal-state pseudogap. The Hall conductivity in particular is of paramount importance, because its sign and magnitude directly reflect the sign of the charge carriers and the size of particle-hole asymmetry effects. An im- portant result in this work is that the Hall and thermal Hall coefficients are always positive above the transition temperature – the fermionic quasiparticles and the Cooper-pair fluctuations both have positive contributions.