Extremely high magnetoresistance and conductivity in the type-II Weyl semimetals WP2 and MoP2

Abstract

The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings can lead to spectacular electronic properties such as large mobilities accompanied by extremely high magnetoresistance. In particular, two closely neighboring Weyl points of the same chirality are protected from annihilation by structural distortions or defects, thereby significantly reducing the scattering probability between them. Here we present the electronic properties of the transition metal diphosphides, WP2 and MoP2, which are type-II Weyl semimetals with robust Weyl points by transport, angle resolved photoemission spectroscopy and first principles calculations. Our single crystals of WP2 display an extremely low residual low-temperature resistivity of 3 nΩ cm accompanied by an enormous and highly anisotropic magnetoresistance above 200 million % at 63 T and 2.5 K. We observe a large suppression of charge carrier backscattering in WP2 from transport measurements. These properties are likely a consequence of the novel Weyl fermions expressed in this compound.

Fermi surface of the Weyl type-II metallic candidate WP2

“…ρ(µ 0 H) ∝ (µ 0 H) λ , with λ = 1.8, for µ 0 H b and λ ≈ 1.8 − 1.9 for the other field orientations. No saturation was observed in ρ(θ, µ 0 H) for fields up to 35 T, in agreement with an earlier report indicating no saturation up 60 T [23]. Hall effect measurements, analyzed via a two-band model and discussed in the SI [24], confirm that WP 2 is a well-compensated conductor, which explains its pronounced magnetoresistivity.…”

“…In WP 2 , the effects of the chiral anomaly associated with its Weyl type-II points are predicted to be observable when fields and currents are parallel to the b-axis which, as already pointed out by Ref. [23], is an experimentally challenging task. Fig.…”

“…Based on DFT calculations it was shown that the electron and hole pockets touch at two inequivalent points located at 0.471 and 0.340 eV below the Fermi energy E F resulting in a total of eight Weyl points across the k x -k y -plane [19]. In addition, a very recent report highlights its unusual electrical transport properties including extremely large magnetoresistivity (MR) possibly related to its underlying Weyl physics [23].…”

Large magnetoresistance in the type-II Weyl semimetal WP2

“…The angle dependence of quantum oscillations agree well with the calculated Fermi surface. 19,48 The calculated Fermi surfaces of WP 2 consist of spaghetti-like hole Fermi surfaces and bow-tie-like electron Fermi surfaces, while the presence of strong spin-orbit coupling leads to splitting of Fermi surfaces. 19,48 The spaghetti-like hole Fermi surface extends along b axis, bends along a axis, while it is flat along c axis, consistent with the quasi-2D enlonged α and β bands in bc plane.…”

“…19,48 The calculated Fermi surfaces of WP 2 consist of spaghetti-like hole Fermi surfaces and bow-tie-like electron Fermi surfaces, while the presence of strong spin-orbit coupling leads to splitting of Fermi surfaces. 19,48 The spaghetti-like hole Fermi surface extends along b axis, bends along a axis, while it is flat along c axis, consistent with the quasi-2D enlonged α and β bands in bc plane. When magnetic field is applied in small angles around b axis, SdH oscillations of γ and η bands are from the orbits across whole electron pockets in ac plane, quasi-2D behavior of γ and η bands can be then attributed to relatively flat wall of electron pockets.…”