Publications

The supercurrent through a quantum point contact coupled to a nanomagnet strongly depends on the dynamics of the nanomagnet's spin. We employ a fully microscopic model to calculate the transport properties of a junction coupled to a spin whose dynamics is modeled as Larmor precession brought about by an external magnetic field and find that the dynamics affects the charge and spin currents by inducing transitions between the continuum states outside the superconducting gap region and the Andreev…

Single molecular magnets (SMM) inspire the research in information storage, spin­tronics, and quantum computation due to their magnetic properties which lie at the interface between classical and quantum mechanical description. Manganese-12-Acetate (Mn12) is the archetypical SMM due to its high spin and long spin relaxation time. While these properties have been observed on bulk samples, the deposition on surfaces has not yet been possible while retaining these characteristics.

In our…

The physics between two magnetic impurities, which interact with each other is very rich and has been the object of numerous theoretical studies. While for weak interaction, the spin of the impurities is suppressed by scattering of conduction electrons, for strong interaction their magnetic properties emerge.

In our experiment, we have studied this model system by attaching a cobalt atom to the tip of our STM. Bringing the atom on the tip close to a cobalt atom on the surface, we could tune…

We study the quantum noise of the electronic current in a double-barrier system with a single resonant level. In the framework of the Landauer formalism, we treat the double barrier as a quantum coherent scattering region that can exchange photons with a coupled electric field, e.g., a laser beam or a periodic ac bias voltage.

As a consequence of the manifold parameters that are involved in this system, a complicated steplike structure arises in the nonsymmetrized current-current…

We study backaction effects of phonon heating due to tunneling electrons on the current noise in atomic-sized junctions. Deriving a generalized kinetic approximation within the extended Keldysh Green’s functions technique, we demonstrate the existence of a characteristic backaction contribution to the noise in case of low external phonon damping. We provide a physically intuitive interpretation of this contribution at large voltage in terms of slow fluctuations of the phonon occupation and show…

We demonstrate for the archetypical organic molecule, benzenedithiol (BDT), incorporated into a mechanically controllable break junction at low temperature, how the nature of the transport and in particular the number of transport channels can be unambiguously deduced from studies of the elastic and inelastic current contributions.

We are able to tune the molecular conformation and thus the transport properties by displacing the nanogap electrodes. We observe stable contacts with low…

The recently discovered spin Seebeck effect refers to a spin current induced by a temperature gradient in a ferromagnetic material. It combines spin degrees of freedom with caloric properties, opening the door for the invention of new, spin caloritronic devices.

Using spin model simulations as well as an innovative, multi-scale micromagnetic framework we show that magnonic spin currents caused by temperature gradients lead to spin transfer torque effects, which can drag a domain wall in a…

The mechanical contact between a thin gold film and a silicon substrate is investigated by ultrafast pump-probe spectroscopy providing quantitative values on the damping time of coherent longitudinal vibrations of the gold film. A distinct increase in damping times is observed when a self-assembled molecular layer is introduced between the gold film and the substrate. The frequency dependence of the damping times is deduced by varying the thickness of the gold films. Experimental results are…