arXiv subjects

M. Ternes

Publications and source records attributed to M. Ternes.

4 recordsLinked to original sources

arXiv2019

Atomic-scale spin sensing with a single-molecule at the apex of a scanning tunneling microscope

Recent advances in scanning probe techniques rely on the chemical functionalization of the probe-tip termination by a single molecule. The success of this approach opens the tantalizing prospect of introducing spin sensitivity through the functionalization by a magnetic molecule. Here, we use a nickelocene-terminated tip (Nc-tip), which offers the possibility of producing spin excitations on the tip apex of a scanning tunneling microscope (STM). We show that when the Nc-tip is a hundred pm away from point contact with a surface-supported object, magnetic effects may be probed through changes in the spin excitation spectrum of nickelocene. We use this detection scheme to simultaneously determine the exchange field and the spin polarization of the sample with atomic-scale resolution. Our findings demonstrate that the Nc-tip is a powerful probe for investigating surface magnetism with STM, from single magnetic atoms to surfaces.

cond-mat.mes-hall↗

arXiv2017

Strong paramagnon scattering in single atom Pd contacts

Among all transition metals, Palladium (Pd) has the highest density of states at the Fermi energy yet does not fulfill the Stoner criterion for ferromagnetism. However, its close vicinity to magnetism renders it a nearly ferromagnetic metal, which hosts paramagnons, strongly damped spin fluctuations. In this letter we compare the total and the differential conductance of mono-atomic Pd and Cobalt (Co) contacts between Pd electrodes. Transport measurements reveal a conductance for Co of 1 $G_0$ , while for Pd we obtain 2 $G_0$. The differential conductance of mono-atomic Pd contacts shows a drop with increasing bias, which gives rise to a peculiar {$Λ$}-shaped spectrum. Supported by theoretical calculations we correlate this finding with the life time of hot quasi-particles in Pd which is strongly influenced by paramagnon scattering. In contrast to this, Co adatoms locally induce magnetic order and transport through single cobalt atoms remains unaffected by paramagnon scattering, consistent with theory.

cond-mat.mes-hall↗

arXiv2015

Exploring the phase diagram of the two-impurity Kondo problem

A system of two exchange-coupled Kondo impurities in a magnetic field gives rise to a rich phase space hosting a multitude of correlated phenomena. Magnetic atoms on surfaces probed through scanning tunnelling microscopy provide an excellent platform to investigate coupled impurities, but typical high Kondo temperatures prevent field-dependent studies from being performed, rendering large parts of the phase space inaccessible. We present an integral study of pairs of Co atoms on insulating Cu2N/Cu(100), which each have a Kondo temperature of only 2.6 K. In order to cover the different regions of the phase space, the pairs are designed to have interaction strengths similar to the Kondo temperature. By applying a sufficiently strong magnetic field, we are able to access a new phase in which the two coupled impurities are simultaneously screened. Comparison of differential conductance spectra taken on the atoms to simulated curves, calculated using a third order transport model, allows us to independently determine the degree of Kondo screening in each phase.

cond-mat.mes-hall↗

arXiv2005

Comment on "Fano Resonance for Anderson Impurity Systems"

In a recent Letter, Luo et al. (Phys. Rev. Lett. 92, 256602 (2004)) analyze the Fano line shapes obtained from scanning tunneling spectroscopy (STS) of transition metal impurities on a simple metal surface, in particular of the Ti/Au(111) and Ti/Ag(100) systems. As the key point of their analysis, they claim that there is not only a Fano interference effect between the impurity d-orbital and the conduction electron continuum, as derived in Ujsaghy et al. (Phys. Rev. Lett. 85, 2557 (2000)), but that the Kondo resonance in the d-electron spectral density has by itself a second Fano line shape, leading to the experimentally observed spectra. In the present note we point out that this analysis is conceptually incorrect. Therefore, the quantitative agreement of the fitted theoretical spectra with the experimental results is meaningless.

cond-mat.str-el↗