Landau level spectroscopy of NbP in Voigt configuration

Niobium phosphide, NbP, is a member of the recently found noncentrosymmetric Weyl semimetal family with 12 Weyl point (WP) pairs with two different type of Weyl points in the first Brillouin zone. When magnetic field is applied along the c axis, all the Weyl pairs are perpendicular to the magnetic field and split the energy bands of all the pairs in a similar way. Experimentally, this case can be readily addressed using infrared magneto-spectroscopy in Faraday geometry. However, when the field is oriented along the a or b axis, the magnetic field is parallel to half of the Weyl pairs and perpendicular to the other half. Here we present magneto-infrared reflection measurements of NbP in the Voigt geometry with B field parallel to the a or b axis. The observed complex structure of inter Landau level transitions will be compared to the calculated dispersion of Landau levels [1] and the measured data in the Faraday geometry.

[1] M. Koshino and I. F. Hizbullah, PRB 93, 045201 (2016)