Partial and macroscopic phase coherences in an underdoped thin film

¹ Research Center for Superconductor Photonics, Osaka University and CREST-JST 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
² Department of Physiscs, Tokyo Institute of Technology and CREST-JST 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
³ Kansai Advanced Research Center, Communication Research Laboratory Kobe 651-2492, Japan

Received: 21 May 2002
Accepted: 25 July 2002

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. It was observed that a superconducting gap and a pseudogap coexist in the superconducting state. The pseudogap locally evolves below  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 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.