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arXiv · 1811.03489

Spectroscopic evidence of nematic fluctuations in LiFeAs

Zhixiang Sun·Pranab Kumar Nag·Steffen Sykora·Jose M. Guevara·Sven Hoffmann·Christian Salazar·Torben Hänke·Rhea Kappenberger·Sabine Wurmehl·Bernd Büchner·Christian Hess
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Abstract

The role of nematic fluctuations in the pairing mechanism of iron-based superconductors is frequently debated. Here we present a novel method to reveal such fluctuations by identifying energy and momentum of the corresponding nematic boson through the detection of a boson-assisted resonant amplification of Friedel oscillations. Using Fourier-transform scanning tunneling spectroscopy, we observe for the unconventional superconductor LiFeAs strong signatures of bosonic states at momentum $q\sim 0$ and energy $Ω\approx8$~meV. We show that these bosonic states survive in the normal conducting state, and, moreover, that they are in perfect agreement with well-known strong above-gap anomalies in the tunneling spectra. Attributing these small-$q$ boson modes to nematic fluctuations we provide the first spectroscopic approach to the nematic boson in an unconventional superconductor.

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Zhixiang Sun, Pranab Kumar Nag, Steffen Sykora, Jose M. Guevara, Sven Hoffmann, Christian Salazar, Torben Hänke, Rhea Kappenberger, Sabine Wurmehl, Bernd Büchner, Christian Hess. 2018-11-08. Spectroscopic evidence of nematic fluctuations in LiFeAs. https://doi.org/10.1103/physrevb.100.024506

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