@article{SessiBiswasBathonetal.2016, author = {Sessi, Paolo and Biswas, Rudro R. and Bathon, Thomas and Storz, Oliver and Wilfert, Stefan and Barla, Alessandro and Kokh, Konstantin A. and Tereshchenko, Oleg E. and Fauth, Kai and Bode, Matthias and Balatsky, Alexander V.}, title = {Dual nature of magnetic dopants and competing trends in topological insulators}, series = {Nature Communications}, volume = {7}, journal = {Nature Communications}, doi = {10.1038/ncomms12027}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172704}, year = {2016}, abstract = {Topological insulators interacting with magnetic impurities have been reported to host several unconventional effects. These phenomena are described within the framework of gapping Dirac quasiparticles due to broken time-reversal symmetry. However, the overwhelming majority of studies demonstrate the presence of a finite density of states near the Dirac point even once topological insulators become magnetic. Here, we map the response of topological states to magnetic impurities at the atomic scale. We demonstrate that magnetic order and gapless states can coexist. We show how this is the result of the delicate balance between two opposite trends, that is, gap opening and emergence of a Dirac node impurity band, both induced by the magnetic dopants. Our results evidence a more intricate and rich scenario with respect to the once generally assumed, showing how different electronic and magnetic states may be generated and controlled in this fascinating class of materials.}, language = {en} } @article{KuegelKarolakKroenleinetal.2018, author = {K{\"u}gel, Jens and Karolak, Michael and Kr{\"o}nlein, Andreas and Serrate, David and Bode, Matthias and Sangiovanni, Giorgio}, title = {Reversible magnetic switching of high-spin molecules on a giant Rashba surface}, series = {npj Quantum Materials}, volume = {3}, journal = {npj Quantum Materials}, doi = {10.1038/s41535-018-0126-z}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230866}, year = {2018}, abstract = {The quantum mechanical screening of a spin via conduction electrons depends sensitively on the environment seen by the magnetic impurity. A high degree of responsiveness can be obtained with metal complexes, as the embedding of a metal ion into an organic molecule prevents intercalation or alloying and allows for a good control by an appropriate choice of the ligands. There are therefore hopes to reach an "on demand" control of the spin state of single molecules adsorbed on substrates. Hitherto one route was to rely on "switchable" molecules with intrinsic bistabilities triggered by external stimuli, such as temperature or light, or on the controlled dosing of chemicals to form reversible bonds. However, these methods constrain the functionality to switchable molecules or depend on access to atoms or molecules. Here, we present a way to induce bistability also in a planar molecule by making use of the environment. We found that the particular "habitat" offered by an antiphase boundary of the Rashba system BiAg2 stabilizes a second structure for manganese phthalocyanine molecules, in which the central Mn ion moves out of the molecular plane. This corresponds to the formation of a large magnetic moment and a concomitant change of the ground state with respect to the conventional adsorption site. The reversible spin switch found here shows how we can not only rearrange electronic levels or lift orbital degeneracies via the substrate, but even sway the effects of many-body interactions in single molecules by acting on their surrounding.}, language = {en} }