nl9b05242_si_001.pdf (1.53 MB)
Topological Band Engineering of Lieb Lattice in Phthalocyanine-Based Metal–Organic Frameworks
journal contribution
posted on 2020-02-25, 15:48 authored by Wei Jiang, Shunhong Zhang, Zhengfei Wang, Feng Liu, Tony LowTopological
properties of the Lieb lattice, i.e., the edge-centered
square lattice, have been extensively studied and are, however, mostly
based on theoretical models without identifying real material systems.
Here, based on tight-binding and first-principles calculations, we
demonstrate the Lieb-lattice features of the experimentally synthesized
phthalocyanine-based metal–organic framework (MPc-MOF), which
holds various intriguing topological phase transitions through band
engineering. First, we show that the MPc-MOFs indeed have a peculiar
Lieb band structure with 1/3 filling, which has been overlooked because
of its unconventional band structure deviating from the ideal Lieb
band. The intrinsic MPc-MOF presents a trivial insulating state, with
its gap size determined by the on-site energy difference (ΔE) between the corner and edge-center sites. Through either
chemical substitution or physical strain engineering, one can tune
ΔE to close the gap and achieve a topological
phase transition. Specifically, upon closing the gap, topological
semimetallic/insulating states emerge from nonmagnetic MPc-MOFs, while
magnetic semimetal/Chern insulator states arise from magnetic MPc-MOFs,
respectively. Our discovery greatly enriches our understanding of
the Lieb lattice and provides a guideline for experimental observation
of the Lieb-lattice-based topological states.