Spin dependent transmission of nickelocene-Cu contacts probed with shot noise

Abstract

The current I through nickelocene molecules and its noise are measured with a low temperature scanning tunneling microscope on a Cu(100) substrate. Density functional theory calculations and many-body modeling are used to analyze the data. During contact formation, two types of current evolution are observed, an abrupt jump to contact and a smooth transition. These data along with conductance spectra (dI/dV ) recorded deep in the contact range are interpreted in terms of a transition from a spin-1 to a spin-1 /2 state that is Kondo screened. Many-body calculations show that the smooth transition is also consistent with a renormalization of spin excitations of a spin-1 molecule by Kondo exchange coupling. The shot noise is significantly reduced compared to the Schottky value of 2eI but no influence of the Kondo effect or spin excitations are resolved. The noise can be described in the Landauer picture in terms of spin-polarized transmission of ≈ 35 % through two degenerate dπ-orbitals of the Nickelocene molecule.

Superconducting Scanning Tunneling Microscope Tip to Reveal Sub-millielectronvolt Magnetic Energy Variations on Surfaces

“…1 (d). This is very different compared to copper surfaces, 38,44 where changes in the molecule-substrate interaction reduce the molecular spin.…”

Current shot noise in atomic contacts: Fe and FeH2 between Au electrodes

“…Investigations of shot noise with a scanning tunneling microscope (STM) are still fairly few in number [25][26][27][28][29][30][31][32]. Here we present results from single Fe atoms on Au(111) surfaces that are hydrogenated in a low-temperature STM.…”

Design Considerations for Oligo(p-Phenyleneethynylene) Organic Radicals in Molecular Junctions

“…For single-molecule junctions, it is much less clear which physical mechanisms are responsible for the observed magnetoresistance behavior. Similarly, the link between Kondo signatures and chemical structures is not fully understood [40], while shot-noise measurements on spin-polarized sys-tems can be related to the difference between majority-and minority-spin transmission [36,37,41,42].…”

“…Molecules display particularly rich behavior when they feature unpaired spins, as present in many transition metal complexes and in organic radicals [20][21][22][23][24][25][26][27][28][29][30]. In the past few years, such molecules have been more and more in the focus of single-molecule break junction experiments with nonmagnetic electrodes, and in particular their response to magnetic fields [11,31], Kondo properties [32][33][34][35] and shot noise resulting from spin correlations [36,37] have been studied. Radicals adsorbed on graphene were also found to enhance the conductance and the Seebeck coefficient of graphene nanoconstrictions based on first-principles simulations [38].…”