Organic Monolayer Protected Topological Surface State

Perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA)/Bi₂Se₃ and Fe/PTCDA/Bi₂Se₃ heterointerfaces are investigated using scanning tunneling microscopy and spectroscopy. The close-packed self-assembled PTCDA monolayer possesses big molecular band gap and weak molecule–substrate interactions, which leaves the Bi₂Se₃ topological surface state intact under PTCDA. Formation of Fe-PTCDA hybrids removes interactions between the Fe dopant and the Bi₂Se₃ surface, such as doping effects and Coulomb scattering. Our findings reveal the functionality of PTCDA to prevent dopant disturbances in the TSS and provide an effective alternative for interface designs of realistic TI devices

Digitized Charge Transfer Magnitude Determined by Metal–Organic Coordination Number

Well-ordered metal–organic nanostructures of Fe-PTCDA (perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride) chains and networks are grown on a Au(111) surface. These structures are investigated by high-resolution scanning tunneling microscopy. Digitized frontier orbital shifts are followed in scanning tunneling spectroscopy. By comparing the frontier energies with the molecular coordination environments, we conclude that the specific coordination affects the magnitude of charge transfer onto each PTCDA in the Fe-PTCDA hybridization system. A basic model is derived, which captures the essential underlying physics and correlates the observed energetic shift of the frontier orbital with the charge transfer

Spin-Dependent Molecule Symmetry at a Pentacene–Co Spinterface

Incorporating spin-polarized scanning tunneling microscopy (SP-STM) measurements and first-principles calculations, we resolve spin-polarized states and consequent features in a pentacene(PEN)–Co hybrid system. Symmetry reduction of PEN clarifies the PEN adsorption site and the Co stacking methods. Near the Fermi energy, the molecular symmetry is spin-dependently recovered and an inversion of spin-polarization in PEN with respect to Co is observed. The experimental findings and calculation results are interpreted by a p_<i>z</i>–d hybridization model, in which spin-dependent bonding–antibonding splitting of molecular orbitals happens at metal–organic spinterfaces