Signatures of superconducting and pseudogap phases in ultrafast transient reflectivity of Ca(Fe0.927Co0.073)2As2
1 Department of Physics, Indian Institute of Science - Bangalore 560012, India
2 Leibniz-Institute for Solid State and materials Research, Dresden - D-01171 Dresden, Germany
Received: 13 September 2013
Accepted: 7 February 2014
We present femtosecond time-resolved pump-probe spectroscopic studies of a pseudogap (PG) along with the superconducting (SC) gap in an overdoped iron pnictide Ca(Fe0.927Co0.073)2As2. It is seen that the temperature evolution of the photo-excited quasiparticle (QP) relaxation dynamics, coherently excited A1g-symmetric optical phonon and two acoustic phonon dynamics behave anomalously in the vicinity of the superconducting transition temperature . A continuous change in the sign of the experimentally measured transient differential reflectivity signal at the zero time delay between the pump and probe pulses at a temperature of is inferred as an evidence of the emergence of the PG phase around that temperature. This behavior is independent of the pump photon energy and occurs for crystals without the spin density wave phase transition.
PACS: 78.47.J- – Ultrafast spectroscopy (<1 psec) / 74.70.Xa – Pnictides and chalcogenides / 74.25.Kc – Phonons
© EPLA, 2014