Self-Assembled H2NC Molecular Lattices as a Platform for Substrate-Tunable Quantum Superlattices

TL;DR

This study explores how self-assembled H2Nc molecular lattices on metal substrates can be tuned electronically, revealing substrate-induced changes in band structure, hybridization, and potential for simulating anisotropic lattice models.

Contribution

It provides a detailed comparison of free-standing and substrate-supported H2Nc monolayers, demonstrating substrate-induced tunability and symmetry breaking effects on electronic properties.

Findings

Substrate adsorption induces hybridization and charge transfer.

Metal substrates can metallize the molecular lattice.

Electronic band structures are tunable via substrate choice.

Abstract

Compared to van der Waals moir\'e systems, molecular assembly has emerged as an exciting alternative platform for superlattice engineering via heterointegration. The electronic properties of the self-assembled square lattice monolayer molecular crystal of metal-free naphthalocyanine (H2Nc), in particular the electronic band dispersion and their tunability by metal substrates, remain less explored. Using density functional theory, supported by angle-resolved photoemission and scanning tunneling microscopy, we compare the electronic structure of a free-standing H2Nc monolayer with that of H2Nc lattice assembled on noble metal substrates. In the freestanding film, we identify both nearly flat, molecule-localized states and more dispersive bands, and we show that each can be compactly described by an anisotropic tight-binding Hamiltonian that yields band-resolved hopping anisotropies. We further reveal wide tunability in the Coulomb interaction and inter-site hopping based on different molecular orbitals. Adsorption on Ag(100) drives strong orbital hybridization, charge transfer, and C2 symmetry breaking, producing partially filled, substrate-mediated dispersive states that metallize the molecular lattice. Orbital analysis identifies C2-even and C2-odd components and maps the spatial pattern of charge redistribution tied to symmetry breaking. Complementary ARPES on H2Nc/Au(111) qualitatively corroborates the predicted dispersion and partial filling. These results clarify how metal substrates convert H2Nc from isolated molecules into a tunable 2D lattice and highlight molecular superlattices as a versatile platform to simulate anisotropic lattice models.