Spin accumulation tuned by vertical strain in ferroelectric type-II Weyl semimetals

The effects of vertical strains on out-of-plane ferroelectric polarizations and on spin accumulations of bulk Tdphase WTe2 and MoTe2 are investigated under the framework of density functional theory. The compressive vertical strain is found to increase the out-of-plane polarization by increasing the uncompensated charges of nonequivalent interlayers while reducing the band gap, which is in contrast with conventional ferroelectrics. The spin accumulation is generally weakened by the compressive vertical strain, suggesting a competitive relationship between the spin-orbit coupling and ferroelectricity. Our work provides an alternative perspective to consider the effect of strains on controlling the ferroelectricity and the spin-orbit coupling of Td-phase WTe2 and MoTe2 for designing new spintronic devices, and a deeper understanding of anisotropic properties and pressureinduced phase transitions of these ferroelectric semimetals.