Particle-hole symmetry in the pseudogap phase of moderately underdoped cuprate high temperature superconductors evidenced from joint density of states analysis

Abstract

In conventional superconductors, the energy scale associated with the superfluid stiffness is much larger compared to the pairing energy and hence, the superconducting transition temperature (Tc) is entirely dictated by the superconducting (SC) energy gap. The phase rigidity of the SC condensate in unconventional superconductors, on the other hand, can be low enough to enable destruction of superconductivity via phase incoherence and persistence of an energy gap even at the absence of macroscopic superconductivity above Tc. This is considered a possible mechanism of the pseudogap (PG) state of cuprate high temperature superconductors (HTSCs). We have investigated the electronic energy ({\omega}) and momentum-separation vector (q) dependence of the joint density of states (JDOS), derived from the autocorrelated Angle Resolved Photoemission Spectroscopy (ARPES) data, from moderately underdoped Bi2Sr2CaCu2O8+{\delta}HTSC samples at temperatures below and above Tc. We found that q-space structure of the constant {\omega} JDOS intensity maps and the dispersions of the JDOS peaks are essentially the same both below and above Tc. Furthermore, the dispersions of the JDOS peaks above Tc are particle-hole symmetric. These observations evince similarity between the nature of the energy gap below and above Tc, which supports preformed pairing scenario for the PG state at least in the moderately underdoped regime.