Subir Sachdev – Harvard
Wednesday, January 14, 2026
Zoom opens: 10:30AM EST
Seminar begins: 10:45AM EST
Detecting a quantum spin liquid in the cuprate superconductors
Following the prescient suggestion of P.~W.~Anderson in 1987, there were numerous early theories of the phases of the cuprate high temperature superconductors as doped quantum spin liquids. However these theories have had difficulties with a number of important observations. I will describe the fractionalized Fermi liquid (FL*) state, proposed in 2002, which dopes quantum spin liquids with gauge-neutral electron-like quasiparticles. The FL* state has a Fermi surface enclosing a non-Luttinger area, and this is made possible by the presence of a quantum spin liquid with fractionalized excitations. Recent angle-dependent magnetoresistance (ADMR) measurements in the lightly-doped `pseudogap’ metal show compelling evidence for holes which can tunnel coherently between square lattice layers, and occupy pocket Fermi surfaces enclosing an area close to that predicted by the FL* theory. A gauge theory for the FL* and neighboring phases in a single-band square lattice Hubbard-type model will be outlined