Collapse of the Pseudogap in Cuprate Superconductors at a Lifshitz Transition

Abstract : We report a fine tuned doping study of strongly overdoped Bi2Sr2CaCu2O8þδ single crystals using electronic Raman scattering. Combined with theoretical calculations, we show that the doping, at which the normal-state pseudogap closes, coincides with a Lifshitz quantum phase transition where the active holelike Fermi surface becomes electronlike. This conclusion suggests that the microscopic cause of the pseudogap is sensitivetotheFermi surfacetopology.Furthermore,we findthatthe superconductingtransitiontemperatureis unaffected by this transition, demonstrating that their origins are different on the overdoped side.