Orbital Symmetry of the Kondo State in Adsorbed FePc Molecules on the Au(110) Metal Surface

The Kondo ground state can arise in surface-supported organometallic systems, such as the 3d transition metal phthalocyanines, as a result of the hybridization of the 3d localized orbitals with the underlying metal substrate electrons. Low-temperature scanning tunneling spectroscopy can identify the Kondo states as a zero-bias anomaly in the differential conductance curves, often localized in close proximity with the 3d metal center. However, the information on the symmetry of the Kondo state, on the exact shape of the spectral function, and on the magnetic state is generally missing from the experimental data. We apply complementary techniques, i.e., scanning tunneling spectroscopy, resonant photoemission spectroscopy, and X-ray magnetic circular dichroism, to identify the Kondo state, the orbital symmetry, and the magnetic moment of Fe-Phthalocyanine chains formed by two structural phases with increasing molecular density: first ×5 and at higher coverage ×7 FePc ordered chain structures assembled on the Au(110) surface. The experimental data suggest the presence of a Kondo state only in the ×5 phase, at lower molecular density, with a Kondo temperature of about 60 K, having parent states with the dxz, dyz symmetry, that cancels the magnetic moment of the molecules at low temperatures.