Magnetic excitations on 2H-NbSe2 - from adatoms and molecules to magnetically coupled nanostructures on a type II superconductor
Final Report Abstract
The transition metal dichalcogenide 2H-NbSe2 is a well-studied type II superconductor with anisotropic s-wave superconductivity, which possesses a strong two-dimensional-like character. Within this project, we explored the local interaction of paramagnetic adatoms, dimers and atomic chains with this particular type of superconductor by means of scanning tunneling microscopy and spectroscopy (STM/STS) at 1.2 K, which offers high energetic and spatial resolution. We resolved Yu-Shiba-Rusinov (YSR) states of single adatoms, which surprisingly depend not only on the atomic adsorption site, but also on the relative position with respect to the charge density wave, present on the surface of 2H-NbSe2 at low temperature. We unveiled a symmetry breaking of the YSR wavefunctions induced by the charge density wave and an energy shift of the YSR bound states depending on the relative position with respect to the charge density wave. Furthermore, we studied the hybridization of YSR states of neighboring Fe atoms. We could provide indications for a coupling of the dimer spins via the spatially extended YSR wavefunctions on the quasi-2D superconductor 2H-NbSe2. Finally, we constructed impurity chains in the dilute limit, that is, at distances were the coupling of neighboring atoms proceeds via the YSR states rather than via direct exchange or superexchange coupling. While the Fe chains presented signatures of YSR band formation and indications for an influence of the CDW modulation on the YSR distribution, there were no signs for zero energy bound states at the chain ends. This indicates that the investigated Fe chains on 2H-NbSe2 were in a topologically trivial phase. Future studies should aim at illuminating the parameter space of impurity coupling on 2H-NbSe2 in terms of coupling strength and mechanisms, as well as impurity spin state.
Publications
- Exploring a Proximity-Coupled Co Chain on Pb(110) as a Possible Majorana Platform. Nano Letters 17, 4473−4477 (2017)
Michael Ruby, Benjamin W. Heinrich, Yang Peng, Felix von Oppen, and Katharina J. Franke
(See online at https://doi.org/10.1021/acs.nanolett.7b01728) - Wave-Function Hybridization in Yu-Shiba-Rusinov Dimers. Physical Review Letters 120, 156803 (2018)
Michael Ruby, Benjamin W. Heinrich, Yang Peng, Felix von Oppen, and Katharina J. Franke
(See online at https://doi.org/10.1103/PhysRevLett.120.156803)
