Campus Units

Physics and Astronomy, Ames Laboratory

Document Type

Article

Publication Version

Accepted Manuscript

Publication Date

2-6-2014

Journal or Book Title

Nature Communications

Volume

5

First Page

3229

DOI

10.1038/ncomms4229

Abstract

Many of the iron pnictides have strongly anisotropic normal-state characteristics, important for the exotic magnetic and superconducting behaviour these materials exhibit. Yet, the origin of the observed anisotropy is unclear. Electronically driven nematicity has been suggested, but distinguishing this as an independent degree of freedom from magnetic and structural orders is difficult, as these couple together to break the same tetragonal symmetry. Here we use time-resolved polarimetry to reveal critical nematic fluctuations in unstrained Ba(Fe1−xCox)2As2. The femtosecond anisotropic response, which arises from the two-fold in-plane anisotropy of the complex refractive index, displays a characteristic two-step recovery absent in the isotropic response. The fast recovery appears only in the magnetically ordered state, whereas the slow one persists in the paramagnetic phase with a critical divergence approaching the structural transition temperature. The dynamics also reveal a gigantic magnetoelastic coupling that far exceeds electron–spin and electron–phonon couplings, opposite to conventional magnetic metals.

Comments

This is a manuscript of an article published as Patz, Aaron, Tianqi Li, Sheng Ran, Rafael M. Fernandes, Joerg Schmalian, Sergey L. Bud’ko, Paul C. Canfield, Ilias E. Perakis, and Jigang Wang. "Ultrafast observation of critical nematic fluctuations and giant magnetoelastic coupling in iron pnictides." Nature Communications 5, (2014): 3229. DOI: 10.1038/ncomms4229. Posted with permission.

Copyright Owner

Macmillan Publishers Limited

Language

en

File Format

application/pdf

Published Version

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