Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 63: Scanning Probe Microscopy and Spin Phenomena

O 63.3: Invited Talk

Wednesday, March 9, 2016, 16:00–16:30, H4

Manipulating spins in single molecules on a superconductor — •Benjamin W. Heinrich — Freie Universität Berlin, Fachbereich Physik, Berlin

The dominant relaxation mechanism for excited spin states on a metal is the exchange of energy and angular momentum with conduction electrons, which results in the creation of electron-hole pairs. A commune strategy to increase the spin lifetime consists in reducing the exchange scattering by the introduction of a thin insulating layer between adsorbate and substrate. We propose an alternative route to stabilize excited spin states, which is based on combining a metal-organic complex with a type I superconductor. The organic ligand decreases the exchange scattering with the superconducting quasiparticles sufficiently to avoid screening. In turn, the superconducting gap prohibits the energy transfer to electron-hole pairs when the excitation energy is smaller than the gap. This increases the excitation lifetime for Fe-octaethylporphyrin-chloride to 10 ns when adsorbed on a superconducting lead substrate, which is orders of magnitude longer than when adsorbed on a metal.

Our strategy will enable even longer lifetimes, perhaps sufficiently long to enable coherent spin manipulation, for systems with a well-chosen anisotropy barrier. It turns out that metal-organic complexes might be suited to achieve this goal. They provide structural flexibility such that the ligand field can be reversibly modified by local potentials, e.g., the tip of the STM, which then modifies the magnetic anisotropy. Fine-tuning of the anisotropy appears to be within reach.