arXiv subjects

Jens Wiebe

Publications and source records attributed to Jens Wiebe.

41 records · Page 3Linked to original sources

arXiv2013

Spin excitations of individual Fe atoms on Pt(111): impact of the site-dependent giant substrate polarization

We demonstrate using inelastic scanning tunneling spectroscopy (ISTS) and simulations based on density functional theory that the amplitude and sign of the magnetic anisotropy energy for a single Fe atom adsorbed onto the Pt(111) surface can be manipulated by modifying the adatom binding site. Since the magnitude of the measured anisotropy is remarkably small, up to an order of magnitude smaller than previously reported, electron-hole excitations are weak and thus the spin-excitation exhibits long lived precessional lifetimes compared to the values found for the same adatom on noble metal surfaces.

cond-mat.mes-hall↗

arXiv2012

Robust Surface Doping of Bi$_2$Se$_3$ by Rb Intercalation

Rubidium adsorption on the surface of the topological insulator Bi$_2$Se$_3$ is found to induce a strong downward band bending, leading to the appearance of a quantum-confined two dimensional electron gas states (2DEGs) in the conduction band. The 2DEGs shows a strong Rashba-type spin-orbit splitting, and it has previously been pointed out that this has relevance to nano-scale spintronics devices. The adsorption of Rb atoms, on the other hand, renders the surface very reactive and exposure to oxygen leads to a rapid degrading of the 2DEGs. We show that intercalating the Rb atoms, presumably into the van der Waals gaps in the quintuple layer structure of Bi$_2$Se$_3$, drastically reduces the surface reactivity while not affecting the promising electronic structure. The intercalation process is observed above room temperature and accelerated with increasing initial Rb coverage, an effect that is ascribed to the Coulomb interaction between the charged Rb ions. Coulomb repulsion is also thought to be responsible for a uniform distribution of Rb on the surface.

cond-mat.mtrl-sci↗

arXiv2011

Analysis of the inelastic contribution to atomic spin excitation spectroscopy

We investigate the dependence of the inelastic spin excitation contribution to scanning tunneling spectroscopy recorded above Fe adsorbates on the InSb(110) surface at subkelvin temperatures, on bulk doping and tunnel junction resistance. To explain our observations, we show how the inelastic contribution depends on the parameters describing the excitation mechanism and tunnel conditions, in the framework of a recently developed model. We conclude that in this particular system of an adsorbate which is strongly relaxed into the substrate, the tip-sample distance dependent by-tunneling has to be taken into account in order to explain the observed variations in the inelastic tunnel spectra.

cond-mat.mes-hall↗

arXiv2010

Itinerant Nature of Atom-Magnetization Excitation by Tunneling Electrons

We have performed single-atom magnetization curve (SAMC) measurements and inelastic scanning tunneling spectroscopy (ISTS) on individual Fe atoms on a Cu(111) surface. The SAMCs show a broad distribution of magnetic moments with $\unit[3.5]{μ_{\rm B}}$ being the mean value. ISTS reveals a magnetization excitation with a lifetime of $\unit[200]{fsec}$ which decreases by a factor of two upon application of a magnetic field of $\unit[12]{T}$. The experimental observations are quantitatively explained by the decay of the magnetization excitation into Stoner modes of the itinerant electron system as shown by newly developed theoretical modeling.

cond-mat.mes-hall↗

arXiv2010

Spin-polarization of platinum (111) induced by the proximity to cobalt nanostripes

We measured a spin polarization above a Pt (111) surface in the vicinity of a Co nanostripe by spin-polarized scanning tunneling spectroscopy. The spin polarization is exponentially decaying away from the Pt/Co interface and is detectable at distances larger than 1 nm. By performing self-consistent ab-initio calculations of the electronic-structure for a related model system we reveal the interplay between the induced magnetic moments within the Pt surface and the spin-resolved electronic density of states above the surface.

cond-mat.mes-hall↗