Bilayer of Indium Phthalocyanine Molecules on Pb(001): Structure and Spin States.

Bilayers of the nonplanar complex indium phthalocyanine (InPc) were studied on superconducting Pb(001) using scanning tunneling microscopy and density functional theory calculations. The structure of the bilayer is drastically different from that of a single layer in terms of the unit cell, the azimuthal orientations of the molecules, and the position of the In ion above (In↑Pc) or below (In↓Pc) the macrocycle. Intriguingly, the presence of the second layer appears to induce a geometric transition of the first layer. Moreover, a Yu-Shiba-Rusinov state reflecting a localized spin is observed above all molecules of the bilayer.