Partial and macroscopic phase coherences in an underdoped

Abstract

A combined study using the time-resolved pump-probe technique and the time domain terahertz transmission spectroscopy has been carried out to investigate the normal-state anomalies in underdoped Bi2Sr2CaCu2O$_{8+{\delta}}$. It was observed that a superconducting gap and a pseudogap coexist in the superconducting state. The pseudogap locally evolves below $T^* \simeq 210$ K simultaneously with the appearance of partial phase coherence with a short lifetime less than 1 ps. With decreasing temperature, the domains with a pseudogap developed and saturated at $T_{\rm S}\sim 95$ K, and the frequency-dependent superconductivity fluctuation appeared as cooperative phenomena among the partial phase-coherent domains. These experimental data show that the development of the partial coherent local domains with a pseudogap has an important role to switch from the partial to the macroscopic phase-coherent state.