  Janus transition metal dichalcogenides, with intrinsic mirror asymmetry,
exhibit a wide array of interesting properties. In this work, we study Janus
monolayers derived from WTe$_2$ using first-principles and tight-binding
calculations. We discover that WSeTe and WSTe are topologically trivial, in
contrast to the parent quantum spin Hall insulator WTe$_2$. Motivated by the
growing interest in non-linear Hall effect, which also requires asymmetric
structures, we investigate the Berry curvature and its dipole in these Janus
systems and find that they exhibit strikingly large values of Berry curvature
dipole, despite being in the topologically trivial phase. We track down the
origin of this behaviour and put forth a low-energy massive Dirac model to
understand the central features of our ab initio computations. Our predictions
introduce Janus monolayers as promising new platforms for exploring as well as
engineering non-linear Hall effect.
