2017

January 10, 2017

We performed a quasiparticle interference study of clean and Mn surface-doped TaAs, a prototypical Weyl semimetal, to test the screening properties as well as the stability of Fermi arcs against Coulomb and magnetic scattering. Contrary to topological insulators, the impurities are effectively screened in Weyl semimetals. We found that adatoms significantly enhance the strength of the signal such that theoretical predictions on the potential impact of Fermi arcs can be unambiguously scrutinized.  The data have been published in Phys. Rev. B 95, 035114 (2017).

Our analysis revealed the existence of three extremely short, previously unknown scattering vectors. Comparison with theory traces them back to scattering events between large parallel segments of spin-split trivial states, strongly limiting their coherence. Overall, our results indicate that intra- as well as inter-Fermi arc scattering are strongly suppressed and may explain why—in spite of their complex multiband structure—­­transport measurements show signatures of topological states in Weyl monopnictides. 

July 7, 2017

Molecules with the same chemical formula but different structural compositions are called tautomers. This transition can be triggered locally by the injection of a tunneling current from a STM tip. In a recent publication we have studied if and to what extent engineered atomic-scale nanostructures can be utilized for the manipulation of remote STM-induced single molecule tautomerization, i.e., by injecting a current not into the molecule to be switched but at a distance of a few nanometers into the surrounding substrate. The experiments nicely show how walls or ellipses engineered from single Ag atoms domp or enhance tautomerization.  The results have been published in Nano Lett. 17, 5106 (2017).