Electronic Structure Manipulation of the Mott Insulator RuCl3 via Single‐Crystal to Single‐Crystal Topotactic Transformation

Abstract The core task for Mott insulators includes how rigid distributions of electrons evolve and how these induce exotic physical phenomena. However, it is highly challenging to chemically dope Mott insulators to tune properties. Herein, we report how to tailor electronic structures of the honeycomb Mott insulator RuCl3 employing a facile and reversible single‐crystal to single‐crystal intercalation process. The resulting product (NH4)0.5RuCl3⋅1.5 H2O forms a new hybrid superlattice of alternating RuCl3 monolayers with NH4+ and H2O molecules. Its manipulated electronic structure markedly shrinks the Mott–Hubbard gap from 1.2 to 0.7 eV. Its electrical conductivity increases by more than 103 folds. This arises from concurrently enhanced carrier concentration and mobility in contrary to the general physics rule of their inverse proportionality. We show topotactic and topochemical interca…