The structurally simplest Fe-based superconductor FeSe with a critical temperature Tc≈ 8.5 K displays a breaking of the four-fold rotational symmetry at a temperature Ts≈87 K. We investigated the electronic properties of FeSe using scanning tunneling microscopy/spectroscopy (STM/S), magnetization, and electrical transport measurements. The results indicated two new energy scales (i) T∗≈ 75 K denoted by an onset of electron-hole asymmetry in STS, enhanced spin fluctuations, and increased positive magnetoresistance; (ii) T∗∗≈ 22 - 30 K, marked by opening up of a partial gap of about 8 meV in STS and a recovery of Kohler's rule. Our results reveal onset of an incipient ordering mode at T∗ and its nucleation below T∗∗. The ordering mode observed here, both in spin as well as charge channels, suggests a coupling between the spins with charge, orbital or pocket degrees of freedom.
@article{arxiv.1508.05224,
title = {Emergence of an incipient ordering mode in FeSe},
author = {Sahana Rößler and Cevriye Koz and Lin Jiao and Ulrich K. Rößler and Frank Steglich and Ulrich Schwarz and Steffen Wirth},
journal= {arXiv preprint arXiv:1508.05224},
year = {2015}
}