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PGI-1 Talk: Prof. Dr. Markus Ternes

Using scanning probe methods to detect and manipulate spins and correlations with atomic precision

27 Jun 2018 11:30
PGI Lecture Hall

PGI-3/RWTH Aachen


Low-temperature scanning tunneling and atomic force microscopes have been very successful tools for studying not only individual atoms and molecules which bear a magnetic spin moment but also complexly coupled systems. The atoms and molecules can be stabilized on surfaces and in junctions and reveal properties that can be adjusted by external stimuli. When these systems interact with the electrons of the supporting electrodes correlated many-particle states can emerge, making them ideal prototypical quantum systems.
In this presentation I will show how effective S = 1 and S = 1/2 model systems of cobalt hydrates (CoHx) on a h-BN/Rh(111) substrate in conjunction with model Hamiltonians can be used to explore this interesting quantum world. I will discuss the manipulation of the total spin of the cobalt complexes by using a H-functionalized scanning probe tip. When the additional hydrogen ligand is brought close to the CoH, switching between a correlated S = 1/2 Kondo state and a S = 1 state in with magnetic anisotropy removes all degeneracies is observed. By simultaneously tracking the exchange force and conductance during the spin change we explore in detail the transition mechanism.
Furthermore, I will outline how the controlled coupling of individual spin systems can lead not only to an energy shift of the eigenstates reminiscent of an externally applied field, but also to a bias asymmetry in the differential conductance due to spin-spin correlations with the environment. These correlations introduce a measurable transport asymmetry wholly unrelated to static spin polarization and external magnetic fields. As an outlook I show how this effect can be used as a method to probe correlated electron materials.


Prof. Dr. Samir Lounis
Phone: +49 2461 61-4068
Fax: +49 2461 61-2850