We review recent progress in the study of quantum oscillations as a tool for uniquely probing low-energy electronic excitations in high-
T
c
cuprate superconductors. Quantum oscillations in the underdoped cuprates reveal that a close correspondence with Landau Fermi-liquid behaviour persists in the accessed regions of the phase diagram, where small pockets are observed. Quantum oscillation results are viewed in the context of momentum-resolved probes such as photoemission, and evidence examined from complementary experiments for potential explanations for the transformation from a large Fermi surface into small sections. Indications from quantum oscillation measurements of a low-energy Fermi surface instability at low dopings under the superconducting dome at the metal–insulator transition are reviewed, and potential implications for enhanced superconducting temperatures are discussed.
Low-energy electronic excitations and band-gap renormalization in CuO