Fig. 4: Schematic diagrams of spin configurations and hole density of a S ligand in a Ni2S10 cluster.
a, b Schematic diagrams of spin configurations in a the Zhang-Rice triplet (ZRT) lattice and b the Zhang-Rice singlet (ZRS) excited lattice under zigzag magnetic order in NiPS3. Large (small) red and blue arrows represent the spin directions of Ni 3 d (S 3p) holes, respectively. Green dotted ellipsoids highlight S2 sites, where two ligand holes exhibit anti-parallel spins, while S1 sites, where the two holes have parallel spins, are depicted for the other S atoms. The magenta circle indicates the locations of ZRS excitations. Due to spin flipping in one of the hole orbitals at the surrounding S sites, the transition from ZRT to ZRS states leads to polarisation reversal. It induces electric dipoles, with the direction indicated by the open arrow inside the magenta circle. c, d Hole density of an S ligand as a function of the long-range ordering field strength h, for the ground ZRT state c and the excited ZRS state d, respectively, as calculated in a Ni2S10 cluster (see details in Ref. 15). FM (AFM) refers to cases where the applied long-range ordering fields at the two Ni sites are parallel (anti-parallel). The differences in hole density between the FM and AFM cases in c and d indicate the charge modulations of self-doped ligand holes at S1 and S2 sites in the ground ZRT state and the polarisation reversal in the excited ZRS state, respectively. (Fig. 4 is remade from Fig. S9 in Ref. 15).
