paper

Scattering Interference Signature of a Pair Density Wave State in the Cuprate Pseudogap Phase

arXiv:2105.06518 · doi:10.1038/s41467-021-26028-x

Abstract

An unidentified quantum fluid designated as the pseudogap (PG) phase is produced by electron-density depletion in the CuO $_{2}$ antiferromagnetic insulator. Current theories suggest that the PG phase may be a pair density wave (PDW) state characterized by a spatially modulating density of electron pairs. Such a state should exhibit a periodically modulating energy gap $I^_{P} (r)$ in real-space, and a characteristic quasiparticle scattering interference (QPI) signature $I^_{P} (q)$ in wavevector space. By studying strongly underdoped Bi $_{2}$ Sr $_{2}$ CaDyCu $_{2}$ O $_{8}$ at hole-density ~0.08 in the superconductive phase, we detect the $8 a_{0}$ -periodic $I^_{P} (r)$ modulations signifying a PDW coexisting with superconductivity. Then, by visualizing the temperature dependence of this electronic structure from the superconducting into the pseudogap phase, we find evolution of the scattering interference signature $I^ (q)$ that is predicted specifically for the temperature dependence of an $8 a_{0}$ -periodic PDW. These observations are consistent with theory for the transition from a PDW state coexisting with d-wave superconductivity to a pure PDW state in the Bi $_{2}$ Sr $_{2}$ CaDyCu $_{2}$ O $_{8}$ pseudogap phase.

30 pages, 5 figures and Supplementary Information