Who: Dr. Markus Ternes, Max Planck Institute for solid state research, Stuttgart, Germany
Place: Donostia International Physics Center
Date: Monday, 24 July 2017, 12:00
In recent years inelastic spin-flip spectroscopy using low-temperature scanning tunneling microscopes has been a very successful tool for studying not only individual spins but also complexly coupled systems. The spin-bearing molecules can be stabilized on surfaces and in junctions with desirable 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 [2, 3] can be used to explore this interesting quantum world. In detail 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 with magnetic anisotropy 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 and might in future be used as a method to probe correlated electron materials.
 P. Jacobson et al., Nature Communications 6, 8536 (2015).
 M. Ternes, New J. Phys. 17, 063016 (2015).
 M. Ternes, Prog. Surf. Sci. 92, 83 (2017).
 P. Jacobson et al., Science Advances 3, e1602060 (2017).
 M. Muenks, et al., Nature Communications 8, 14119 (2017).