  In the quest to find a favourable triatomic molecule for detecting electric
dipole moment of an electron (eEDM), we identify mercury hydroxide (HgOH) as an
extremely attractive candidate from both experimental and theoretical
viewpoints. Our calculations show that there is a four-fold enhancement in the
effective electric field of HgOH compared to the recently proposed ytterbium
hydroxide (YbOH) [Phys. Rev. Lett. 119, 133002 (2017)] for eEDM measurement.
Thus, in the (010) bending state associated with the electronic ground state,
it could provide better sensitivity than YbOH from a theoretical point of view.
We have also investigated the potential energy curve and permanent electric
dipole moment of HgOH, which lends support for its experimental feasibility.
Moreover, we propose that it is possible to laser cool the HgOH molecule by
adopting the same technique as that in the diatomic polar molecule, HgF, as
shown in [Phys. Rev. A 99, 032502 (2019)].
