Abstract
The pseudogap state in underdoped cuprates shows many very anomalous features. Among them are an extended temperature region of pairing fluctuations above the superconducting transition temperature and an unusual giant phonon anomaly in the same temperature and hole density range. A recent theoretical proposal that ascribes these anomalies to the presence of strong phase fluctuations related to a Leggett mode, is summarised.
Acknowledgements
I am very grateful to Ye-Hua Liu for his close and important collaboration on this work. The input from Robert Konik and Fu Chun Zhang on this project is also gratefully acknowledges.
Notes
No potential conflict of interest was reported by the author.