Observation of pseudogap-like feature above Tc in LiFeAs and (Ba0.6K0.4)Fe2As2 by ultrafast optical measurement

TL;DR

This study uses ultrafast optical measurements to detect pseudogap-like features above the superconducting transition temperature in LiFeAs and (Ba0.6K0.4)Fe2As2, suggesting a universal phenomenon linked to magnetic fluctuations in iron-based superconductors.

Contribution

First observation of pseudogap-like features above Tc in these materials using ultrafast optical techniques, indicating a common magnetic fluctuation origin.

Findings

Pseudogap at ~55 K in LiFeAs above Tc=15 K

Pseudogap at ~90 K in (Ba0.6K0.4)Fe2As2 above Tc=36 K

Pseudogap feature is likely universal in iron-based superconductors

Abstract

We utilize ultrafast optical measurement to study the quasiparticle relaxation in stoichiometric LiFeAs and nearly optimally doped (BaK)Fe2As2 crystals. According to our temperature-dependent studies of LiFeAs, we have observed pseudogap-like feature at onset temperature of ~ 55 K, which is above Tc = 15 K. In addition, the onset temperature of pseudogap ~90K was also observed in Ba0.6K0.4Fe2As2 (Tc = 36 K). Our findings seem implying that the pseudogap feature, which is due to antiferromagnetic fluctuations, is universal for the largely studied 11, 111, 122, and 1111 iron-based superconductors.