Phase-Incoherent Superconductivity in the Pseudogap Phase of Cuprates Revealed by Particle-Hole Symmetric Joint Density of States

Unlike conventional superconductors, cuprate high-temperature superconductors (HTSCs) exhibit an energy gap that persists well above the superconducting transition temperature (T_c), known as the pseudogap state. The microscopic origin of this energy gap and its relationship to the particle-hole symmetric superconducting energy gap remain among the most fundamental open questions in condensed matter physics. In this work, we performed angle-resolved photoemission spectroscopy (ARPES) measurements on moderately underdoped Bi₂Sr₂CaCu₂O_8+δ cuprate HTSC samples across T_c to investigate the nature of the energy- and momentum-separation-vector-dependent joint density of states (JDOS). The JDOS at a given energy was obtained by applying an autocorrelation technique to the corresponding ARPES single-particle spectral intensity map. Our analysis reveals that the overall JDOS structure and the dispersions of its peaks remain essentially unchanged both above and below T_c. Moreover, the JDOS peak dispersions exhibit particle-hole symmetry, indicating a strong correspondence between the gap features in the superconducting and pseudogap phases. These observations support the theoretical scenario in which the pseudogap phase represents a phase-incoherent superconducting state, at least in the moderately underdoped regime.