Effect of Magnetic Ordering on Charge Dynamics in Weyl Semimetals PrAlX (X=Si,Ge)*

PrAlSi and PrAlGe are Weyl semimetal with ferromagnetic ground state, allowing for studying the potential coupling between magnetism and Dirac fermions. We performed reflectance measurements on single crystals of both PrAlSi and PrAlGe, in the range of 10 meV to 3 eV, at temperatures between 300 K and 5 K.

 

Involving Kramers-Kronig transformation, we obtained and discuss here optical conductivity σ₁(ω) and other optical functions of interest (dielectric and loss functions, spectral weight). In both compounds, but more evidently in PrAlSi, we observed significant spectral regions of linear optical conductivity with frequency, i.e. σ₁(ω)∝ω, consistent with Weyl bands predicted from band structure calculations. More importantly, we could observe and map gradual evolution of σ₁(ω) across the magnetic phase transition. Possible origins and implications of these changes will also be addressed.