Detection of Orbital Fluctuations Above the Structural Transition   Temperature in the Iron-Pnictides and Chalcogenides

H. Z. Arham; C. R. Hunt; W. K. Park; J. Gillett; S. D. Das; S. E.; Sebastian; Z. J. Xu; J. S. Wen; Z. W. Lin; Q. Li; G. Gu; A. Thaler; S. Ran,; S. L. Bud'ko; P. C. Canfield; D. Y. Chung; M. G. Kanatzidis; L. H. Greene

arXiv:1201.2479·cond-mat.supr-con·November 26, 2016

Detection of Orbital Fluctuations Above the Structural Transition Temperature in the Iron-Pnictides and Chalcogenides

H. Z. Arham, C. R. Hunt, W. K. Park, J. Gillett, S. D. Das, S. E., Sebastian, Z. J. Xu, J. S. Wen, Z. W. Lin, Q. Li, G. Gu, A. Thaler, S. Ran,, S. L. Bud'ko, P. C. Canfield, D. Y. Chung, M. G. Kanatzidis, L. H. Greene

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TL;DR

This study uses point contact spectroscopy to investigate orbital fluctuations in iron-based superconductors, revealing their presence above structural transition temperatures and their correlation with resistive anisotropy, doping, and temperature.

Contribution

It provides new insights into the temperature-dependent orbital fluctuations in AEFe2As2 and Fe1+yTe, and their relation to resistive anisotropy and doping effects.

Findings

01

Orbital fluctuations are detected above T_S in Sr and Ba compounds.

02

Orbital fluctuations start below T_S in Ca compounds.

03

Doping influences the presence and suppression of orbital fluctuations.

Abstract

We use point contact spectroscopy to probe $AEF e_{2} A s_{2}$ ( $AE = Ca, Sr, Ba$ ) and $F e_{1 + y} Te$ . For $AE = Sr, Ba$ we detect orbital fluctuations above $T_{S}$ while for AE=Ca these fluctuations start below $T_{S}$ . Co doping preserves the orbital fluctuations while K doping suppresses it. The fluctuations are only seen at those dopings and temperatures where an in-plane resistive anisotropy is known to exist. We predict an in-plane resistive anisotropy of $F e_{1 + y} Te$ above $T_{S}$ . Our data are examined in light of the recent work by W.-C. Lee and P. Phillips (arXiv:1110.5917v2). We also study how joule heating in the PCS junctions impacts the spectra. Spectroscopic information is only obtained from those PCS junctions that are free of heating effects while those PCS junctions that are in the thermal regime display bulk resistivity phenomenon.

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