Effect of topology on quasi-particle interactions in the Weyl semimetal WP$_2$

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 βphase, a Weyl semimetal with a giant magneto-resistance, shows a larger intensity of electronic Raman scattering compared to the topologically trivial α-phase. This intensity sharply drops 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 non-topological α-phase shows more pronounced signatures of electron-phonon interaction. Here there exist generally enlarged phonon linewidths 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. Both interband and intraband electronic fluctuations are involved in these effects. Their dependence on symmetry as well as momentum conservation are critical ingredients to understand this interplay.

Evidence for dominant phonon-electron scattering in Weyl semimetal WP$_{2}$

“…The full polarization dependence yields the mode assignments shown in Fig. 1a, which are consistent with previous studies 20,21 (Supplemental Table 1). In Fig.…”

“…Such behavior requires an overlap in energy between an electronic continuum and the discrete phonon state. However the electronic Raman scattering (a quasi-elastic peak) 21 appears below the energy of the optical phonons. In Fig.…”

Deformation of graphene sheet: Interaction of fermions with phonons

“…Considering deformations of the honeycomb lattice as an elastic field of phonons we reduce the problem to the interaction of fermions with phonons and define the corresponding Hamiltonian. We analyze the emerging Z 2 anomaly of this model and show how phonons may produce an anomalous current, which, in principle, can be detected experimentally [20,21].…”