  We construct the most generic Hamiltonian of the $8Pmmn$ structure of
borophene sheet in presence of spin-orbit, as well as background electric and
magnetic fields. In addition to spin and valley Hall effects, this structure
offers a framework to conveniently manipulate the resulting "tilt" of the Dirac
equation by applying appropriate electric fields. Therefore, the tilt can be
made space-, as well as time-dependent. The border separating the low-field
region with under-tilted Dirac fermions from the high-field region with
over-tilted Dirac fermions will correspond to a black-hole horizon. In this
way, space-time dependent electric fields can be used to design the metric of
the resulting space-time felt by electrons and holes satisfying the tilted
Dirac equation. Our platform offers a way to generate analogues of
gravitational waves by electric fields (instead of mass sources) which can be
detected in solid state spectroscopies as waves of enhanced superconducting
correlations.
