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Abstract

We compare two crystallographic phases of the low-dimensional WP2 to better understand features of electron-electron and electron-phonon interactions in topological systems. The topological beta phase, a Weyl semimetal with a giant magnetoresistance, shows a larger intensity of electronic Raman scattering compared to the topologically trivial alpha phase. This intensity collapses for T < T* = 20 K, which evidences a crossover in the topological phase from marginal quasiparticles to a coherent low-temperature regime. In contrast, the topologically trivial alpha phase shows more pronounced signatures of electron-phonon interaction, i.e., an enhanced phonon linewidth and deviations from conventional anharmonicity in an intermediate-temperature regime. These effects provide evidence for an interesting interplay of electronic correlations and electron-phonon coupling. Interband and intraband electronic fluctuations can be distinguish by the energy range of electronic Raman scattering and their temperature dependence. Furthermore, we demonstrate a decisive dependency on symmetry that is critical to understand their interplay.