Single-Component Molecular Material Hosting Antiferromagnetic And Spin-Gapped Mott Subsystems

We investigated a system based solely on a single molecular species, Cu(tmdt)(2), accommodating d and pi orbitals within the molecule. C-13 nuclear magnetic resonance measurements captured singlet-triplet excitations of pi spins indicating the existence of a pi-electron-based spin-gapped Mott insulating subsystem, which has been hidden by the large magnetic susceptibility exhibited by the d spins forming antiferromagnetic chains. The present results demonstrate a unique hybrid Mott insulator composed of antiferromagnetic and spin-singlet Mott subsystems with distinctive dimensionalities.