Large enhancement of Berry-curvature dipole in monolayer W_0.5Mo_0.5Te₂

WTe₂ and MoTe₂ monolayers provide a rich atomically thin platform to explore topological physics, electrically switchable circular photogalvanic effect, rectification, and quantum nonlinear Hall effects. For realization of the nonlinear quantum phenomena, a nonzero Berry-curvature dipole (BCD) is required, which has been demonstrated in pristine WTe₂ and MoTe₂ monolayers [1-4]. In this work, we theoretically design a new monolayer W_0.5Mo_0.5Te₂ using the pristine T_d-WTe₂ and T_d-MoTe₂ monolayers [5]. We confirm the dynamical, elastic, and mechanical stability of W_0.5Mo_0.5Te₂ monolayer by phonon and elastic constants calculations. Our electronic band structure calculations reveal the presence of a relatively much smaller bandgap near the Fermi energy compared to that of in pristine T_d-WTe₂ and T_d-MoTe₂ monolayers. Such a narrow bandgap leads to divergence of Berry curvature near the Fermi energy yielding a large enhancement of BCD in W_0.5Mo_0.5Te₂ monolayer, as predicted by our first-principles calculations.

[1] You et al., Phys. Rev. B 98, 121109 (2018).

[2] Zhang et al., 2D Materials 5, 044001 (2018).

[3] S.-Y. Xu et al., Nat. Phys. 14, 900 (2018).

[4] Ma et al., Nature 565, 337–342 (2019).

[5] Karki et al., arXiv:2109.08725 (2021).