Competing energy scales in high-temperature superconductors: Ultrafast pump-probe studies

Abstract

We present a review of photoexcited quasiparticle dynamics of cuprate and pnictide high-temperature superconductors in regimes (temperature, doping) where different phases such as superconductivity, spin-density-wave (SDW) and pseudogap phases coexist or compete with one another. We start with the overdoped cuprate superconductor Y1-xCax Ba2Cu3O7-δ, where the superconducting gap and pseudogap coexist in the superconducting state. In another cuprate Tl2Ba2Ca2Cu3Oy, we ob- serve a competition between SDW and superconducting orders deep in the superconducting state. Finally, in the underdoped iron pnictide superconductor (Ba,K)Fe2As2, SDW order forms at 85 K, followed by superconductivity at 28 K. We also find the emergence of a normal-state order that suppresses SDW at a temperature T * ~ 60 K and argue that this normal-state order is a precursor to superconductivity. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)The complex pucomplexesle of phases that can exist, co-exist, or compete in strongly correlated electron materials is among the greatest opportunities for progressing our understanding of solids state physics today. With this Review@RRL we are pleased to introduce an article category that, in line with the focus of pss (RRL), aims at highlighting most recent new developments in a particularly active field. Here the authors explain the insight that time-resolved spectroscopy brought for the study of photoexcited quasiparticle dynamics, discussing examples of cuprate and pnictide high-temperature superconductors in regimes where different phases such as superconductivity, spin-density-wave and pseudogap phases coexist or compete with one another. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.