Ultrafast structural dynamics of the orthorhombic distortion in the Fe-pnictide parent compound BaFe2As2.

L Rettig,S Grübel,J Rittmann,S L Johnson,P Beaud,S O Mariager,J A Johnson,A Ferrer,T Wolf,U Staub,G Ingold

doi:10.1063/1.4947250

Abstract

Using femtosecond time-resolved hard x-ray diffraction, we investigate the structural dynamics of the orthorhombic distortion in the Fe-pnictide parent compound BaFe2As2. The orthorhombic distortion analyzed by the transient splitting of the (1 0 3) Bragg reflection is suppressed on an initial timescale of 35 ps, which is much slower than the suppression of magnetic and nematic order. This observation demonstrates a transient state with persistent structural distortion and suppressed magnetic/nematic order which are strongly linked in thermal equilibrium. We suggest a way of quantifying the coupling between structural and nematic degrees of freedom based on the dynamics of the respective order parameters.

Highlights

The close proximity of different types of order in the complex phase diagram of the Fe pnictide high-TC superconductors bears witness of the importance of electronic, magnetic, and structural degrees of freedom for their properties
Using femtosecond time-resolved hard x-ray diffraction, we investigate the structural dynamics of the orthorhombic distortion in the Fe-pnictide parent compound BaFe2As2
We suggest a way of quantifying the coupling between structural and nematic degrees of freedom based on the dynamics of the respective order parameters

Summary

Introduction

The close proximity of different types of order in the complex phase diagram of the Fe pnictide high-TC superconductors bears witness of the importance of electronic, magnetic, and structural degrees of freedom for their properties. A strong biquadratic coupling of the structural and magnetic transitions has been proposed based on the temperature behavior of the respective order parameters, and a nematic phase of local orbital and magnetic anisotropy has been shown to persist in the temperature range between the Neel temperature TN and the structural transition temperature TS.. A strong biquadratic coupling of the structural and magnetic transitions has been proposed based on the temperature behavior of the respective order parameters, and a nematic phase of local orbital and magnetic anisotropy has been shown to persist in the temperature range between the Neel temperature TN and the structural transition temperature TS.5–7 This nematic order was suggested to be the driving force of the structural transition, yet a structural origin of the nematic order was discussed.. A strong biquadratic coupling of the structural and magnetic transitions has been proposed based on the temperature behavior of the respective order parameters, and a nematic phase of local orbital and magnetic anisotropy has been shown to persist in the temperature range between the Neel temperature TN and the structural transition temperature TS. This nematic order was suggested to be the driving force of the structural transition, yet a structural origin of the nematic order was discussed.

Results

Discussion

Conclusion