Fig. 3: STM topographic signatures of MnPc molecules with spin S = 3/2 on monolayer 1T-NbSe₂.

a Schematic representation of atomic-scale manipulation and detection technique. The STM tip can reversibly manipulate the MnPc molecule on the top and hollow sites of CDW lattice in monolayer 1T-NbSe₂, and can efficiently detect, simultaneously, the interaction between a QSL state (monolayer 1T-NbSe₂) and a local magnetic impurity with S = 3/2 spin (MnPc). b Atomic structure of MnPc molecule, including a center Mn ion and the surrounding Pc ligand. c d-orbitals and spin configurations of the center Mn ion in MnPc. d, e STM images of a MnPc molecule on monolayer 1T-NbSe₂, with the central Mn atom of the molecule locating on the top and hollow sites of the CDW lattice, respectively (V_b = −3.5 V, I_t = 10 pA). The atomic structures of MnPc molecule are superimposed onto the STM images, exhibiting a fourfold symmetry.