Helicity protected ultrahigh mobility Weyl fermions in NbP

Understand

Non-centrosymmetric transition metal monopnictides, including TaAs, TaP, NbAs, and NbP, are emergent topological Weyl semimetals (WSMs) hosting exotic relativistic Weyl fermions.

• In this letter, we elucidate the physical origin of the unprecedented charge carrier mobility of NbP, which can reach $1\times10^{7}$ cm $^{2}$V$^{-1}$s$^{-1}$ at 1.5 K.
• Angle- and temperature-dependent quantum oscillations, supported by density function theory calculations, reveal that NbP has the coexistence of p- and n-type WSM pockets in the $k_{z}$=1.16$\pi$/c plane (W1-WSM) and in the $k_{z}$=0 plane near the high symmetry points $\Sigma$ (W2-WSM), respectively.
• Uniquely, each W2-WSM pocket forms a large dumbbell-shaped Fermi surface (FS) enclosing two neighboring Weyl nodes with the opposite chirality.