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arXiv · 1908.11361

Raman response in the nematic phase of FeSe

Mattia Udina·Marco Grilli·Lara Benfatto·Andrey V. Chubukov
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Abstract

Raman experiments on bulk FeSe revealed that the low-frequency part of $B_{1g}$ Raman response $R_{B_{1g}}$, which probes nematic fluctuations, rapidly decreases below the nematic transition at $T_n \sim 85$K. Such behavior is usually associated with the gap opening and at a first glance is inconsistent with the fact that FeSe remains a metal below $T_n$, with sizable hole and electron pockets. We argue that the drop of $R_{B_{1g}}$ in a nematic metal comes about because the nematic order drastically changes the orbital content of the pockets and makes them nearly mono-orbital. In this situation $B_{1g}$ Raman response gets reduced by the same vertex corrections that enforce charge conservation. The reduction holds at low frequencies and gives rise to gap-like behavior of $R_{B_{1g}}$, in full agreement with the experimental data.

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Mattia Udina, Marco Grilli, Lara Benfatto, Andrey V. Chubukov. 2019-08-29. Raman response in the nematic phase of FeSe. https://doi.org/10.1103/physrevlett.124.197602

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