Quantum Cafe: Subir Sachdev

Title: Fractionalized Femi Liquid (FL) Theory of the Cuprate Pseudogap, and its Connections to the Cuprate Phase Diagram

Abstract: The pseudogap metal phase of the cuprate high-temperature superconductors has been a long-standing puzzle, marked by seemingly contradictory features in its electronic spectrum. While photoemission and scanning tunneling microscopy (STM) experiments reveal a truncated “Fermi arc,” recent high-field magnetotransport studies provide compelling evidence for small hole pockets. I propose a unified framework for these observations by describing the pseudogap phase as a fractionalized Fermi liquid (FL*), consisting of hole-pocket Fermi surfaces coexisting with a quantum spin liquid background. In the FL* state with doping p, each pocket was predicted to have fractional area of p/8, in excellent agreement with the Yamaji angle observed in a recent magnetotransport experiment.

As time permits, I will connect this theory to numerous other features of the cuprate phase diagram, including low temperature quantum oscillations, the ‘fan and foot’ regime of strange metal behavior, and the structure of vortex cores in the superconducting state.