Anisotropic Fano resonance in the Weyl semimetal candidate LaAlSi

Kunyan Zhang, Tong Wang, Xiaoqi Pang, Fei Han, Shun Li Shang, Nguyen T. Hung, Zi Kui Liu, Mingda Li, Riichiro Saito, Shengxi Huang

Research output: Contribution to journalArticlepeer-review

Abstract

Topological Weyl semimetal (WSM) is a solid-state realization of chiral Weyl fermions, whose phonon behaviors provide in-depth knowledge of their electronic properties. In this work, anisotropic Fano resonance is observed in a type-II WSM candidate LaAlSi by polarized Raman spectroscopy. The asymmetric line shape occurs for the B12 phonon mode of LaAlSi only for 488- and 532-nm laser excitations but not for 364-, 633-, and 785-nm excitations, suggesting the excitation selectivity. The asymmetry, frequency, and linewidth of the B12 phonon mode, along with the spectral background, all show fourfold rotational symmetry as a function of the polarization angle in the polarized Raman spectra. While the shift of Raman frequency in a metal or semimetal is typically attributed to Kohn anomaly, here we show that the anisotropic frequency shift in LaAlSi cannot be explained by the effect of Kohn anomaly, but potentially by the anisotropic scattering background of Fano resonance. Origins of the excitation-energy dependence and anisotropic behavior of the Fano resonance are discussed by the first-principles calculated electronic band structure and phonon dispersion.

Original languageEnglish (US)
Article number235162
JournalPhysical Review B
Volume102
Issue number23
DOIs
StatePublished - Dec 30 2020

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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