Effect of uniaxial stress on the electronic band structure of NbP

Abstract

The Weyl semimetal NbP exhibits a very small Fermi surface consisting of two electron and two hole pockets, whose fourfold degeneracy in k space is tied to the rotational symmetry of the underlying tetragonal crystal lattice. By applying uniaxial stress, the crystal symmetry can be reduced, which successively leads to a degeneracy lifting of the Fermi-surface pockets. This is reflected by a splitting of the Shubnikov-de Haas frequencies when the magnetic field is aligned along the c axis of the tetragonal lattice. In this study, we present the measurement of Shubnikovde Haas oscillations of single-crystalline NbP samples under uniaxial tension, combined with stateof-the-art calculations of the electronic band structure. Our results show qualitative agreement between calculated and experimentally determined Shubnikov-de Haas frequencies, demonstrating the robustness of the band-structure calculations upon introducing strain. Furthermore, we predict a significant shift of the Weyl points with increasing uniaxial tension, allowing for an effective tuning to the Fermi level at only 0.8 % of strain along the a axis.

Strong anisotropy of electron-phonon interaction in NbP probed by magnetoacoustic quantum oscillations

“…109) with the lattice parameters a = b = 3.3324(2) A and c = 11.13705(7) A [25]. A singlecrystalline sample of NbP was grown using chemical vapor transport reactions; the sample has also been used in our previous work [23] for the determination of the elastic moduli. For acoustic modes propagating along one of the main axes, the sample was cut accordingly to a cuboid-shape of dimension 1.92×1.80×0.88 mm 3 .…”

“…It exhibits a very small and highly anisotropic Fermi surface, consisting of intercalated spin-split pairs of electron and hole pockets due to spin-orbit coupling [18]. The small Fermi surface gives rise to pronounced QO of relatively low frequencies, which have so far been observed in magnetization [18][19][20], electrical resistivity [21][22][23][24], Hall resistivity [21,23], thermal conductivity [19], thermopower [19], and heat capacity [19]. The superposition of QO originating from different extremal Fermi-surface orbits yield a rich Fourier spectrum, especially when H is aligned along the c axis of the tetragonal lattice and the extremal orbits are the smallest.…”

“…The peaks in the Fourier spectra could be assigned to orbits via comparison of experimental data to ab initio density functional theory (DFT) calculations [18], however, ambiguities due to the limited resolution and the broadness of the Fourier peaks remained. In a recent study by some of the authors [23], the evolution of the Fermi surface upon direct application of uniaxial stress along the a axis has been probed by means of Shubnikov-de Haas (SdH) oscillations in the electrical resistivity. These experiments revealed a strong strain dependence of the SdH oscillations, which, besides the additional information regarding the orbit assignments, also render NbP a promising platform for studying magnetoacoustic QO.…”

Skyrmion generation and perpendicular magnetic anisotropy modification in Heusler alloy ultrathin films

“…What's more, there is a 3.27% lattice mismatch between Co 2 MnGa and the MgO substrate. Though the stress in the 50 nm film is almost fully relaxed due to the post-annealing, there could be a tetragonal distortion at low thickness which might induce an energy shift of the Weyl nodes [178]…”

“…What's more, there is a 3.27% lattice mismatch between Co 2 MnGa and the MgO substrate. Though the stress in the 50 nm film is almost fully relaxed due to the post-annealing, there could be a tetragonal distortion at low thickness which might induce an energy shift of the Weyl nodes[178] or shift the electron density-of-states[179]. Note the very different maxima used in the scales ofFigures 6.7(a) -(d) vs Figures 6.7(e) -(f), so that the main features can be seen in Figures 6.7(a) -(d), and the very large spikes can be seen in Figures 6.7(e) -(f).…”