Abstract
The role of nematic fluctuations in the pairing mechanism of iron-based superconductors is frequently debated. Here, we present a method to reveal such fluctuations by identifying the 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 and energy 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- boson modes to nematic fluctuations, we provide a spectroscopic approach to the nematic boson in an unconventional superconductor.
8 More- Received 8 November 2018
- Revised 8 April 2019
DOI:https://doi.org/10.1103/PhysRevB.100.024506
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