  By combining exotic band dispersion with nontrivial band topology, an
interesting type of band structure, namely the flat chern band (FCB), has
recently been proposed to spawn high-temperature fractional quantum hall
states. Despite the proposal of several theoretical lattice models, however, it
remains a doubt whether such a "romance of flatland" could exist in a real
material. Here, we present a first-principles design of a two-dimensional (2D)
Indium-Phenylene Organometallic Framework (IPOF) that realizes a nearly FCB
right around the Fermi level by combining lattice geometry, spin-orbit coupling
and ferromagnetism. An effective four-band model is constructed to reproduce
the first-principles results. Our design in addition provides a general
strategy to synthesize topologically nontrivial materials in virtue of organic
chemistry and nanotechnology.
