Evidence of a coupled electron-phonon liquid in NbGe\(_2\)

• Published in: arXiv.org
• Main Authors: Hung-Yu, Yang, Yao, Xiaohan, Plisson, Vincent, Mozaffari, Shirin, Scheifers, Jan P, Aikaterini Flessa Savvidou, McCandless, Gregory T, Padlewski, Mathieu F, Putzke, Carsten, Moll, Philip J W, Chan, Julia Y, Balicas, Luis, Burch, Kenneth S, Tafti, Fazel
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 02.03.2021
• Subjects: Electron phonon interactions; Electrons; Elementary excitations; Fermi liquids; Momentum; Phonons; Raman spectra; Symmetry; Temperature dependence; Transition metals; Transport properties
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2103.01515

Whereas electron-phonon scattering typically relaxes the electron's momentum in metals, a perpetual exchange of momentum between phonons and electrons conserves total momentum and can lead to a coupled electron-phonon liquid with unique transport properties. This theoretical idea was proposed decades ago and has been revisited recently, but the experimental signatures of an electron-phonon liquid have been rarely reported. We present evidence of such a behavior in a transition metal ditetrelide, NbGe\(_2\), from three different experiments. First, quantum oscillations reveal an enhanced quasiparticle mass, which is unexpected in NbGe\(_2\) due to weak electron-electron correlations, hence pointing at electron-phonon interactions. Second, resistivity measurements exhibit a discrepancy between the experimental data and calculated curves within a standard Fermi liquid theory. Third, Raman scattering shows anomalous temperature dependence of the phonon linewidths which fits an empirical model based on phonon-electron coupling. We discuss structural factors, such as chiral symmetry, short metallic bonds, and a low-symmetry coordination environment as potential sources of coupled electron-phonon liquids.