Observation of a critical charge mode in a strange metal.

Kobayashi, Hisao; Sakaguchi, Yui; Kitagawa, Hayato; Oura, Momoko; Ikeda, Shugo; Kuga, Kentaro; Suzuki, Shintaro; Nakatsuji, Satoru et al. · Science · 2023

basic_science · Level V

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Abstract

Understanding the strange metallic behavior that develops at the brink of localization in quantum materials requires probing the underlying electronic charge dynamics. Using synchrotron radiation-based Mössbauer spectroscopy, we studied the charge fluctuations of the strange metal phase of β-YbAlB<sub>4</sub> as a function of temperature and pressure. We found that the usual single absorption peak in the Fermi-liquid regime splits into two peaks upon entering the critical regime. We interpret this spectrum as a single nuclear transition, modulated by nearby electronic valence fluctuations whose long time scales are further enhanced by the formation of charged polarons. These critical charge fluctuations may prove to be a distinct signature of strange metals.