Paula Obladen | Searcharxiv

arXiv2026

Scanning Tunneling Microscopy in high vectorial magnetic fields

The Scanning Tunneling Microscope (STM) is a powerful instrument to study electronic density of states at surfaces down to atomic scale. Many interesting samples require studying variations as a function of the magnetic field, which is most often applied perpendicular to the surface. Conventional STM designs make it challenging to perform measurements when the magnetic field must be applied in other directions. Here we present a new STM setup installed on a rotatable platform. We have designed and built a new STM, which is small enough to allow for full rotation on a space with a diameter of 37 mm, well below the available space within many magnets. We show that the new rotatable STM setup preserves the performance of state-of-the-art STMs in terms of noise and accuracy. Our new approach significantly enhances control over the direction of the applied magnetic field and opens exciting new possibilities to study quantum materials.

cond-mat.supr-con↗

arXiv2026

Conductance of atomic size contacts of Ag and Au at high magnetic fields

Electronic conduction at the atomic scale can be described by Landauer's formalism. In single atom point contacts of noble metals like Au and Ag, there is just one channel open between both electrodes and the conductance is very close to the quantum of conductance $G \approx G_0=\frac{2e^2}{h}$, with the factor of two coming from spin degeneracy. The magnetoconductivity of atomic size contacts has been studied for numerous systems, unveiling local Kondo screening, magnetic order and spin-polarized currents. However, these have been mostly performed in elements with multiple open conduction channels where $G$ differs from $G_0$. The realization of a magnetically active conductor with a single open channel remains difficult to achieve. Here we present measurements of the electronic conductance of single channel Au and Ag atomic-size contacts in magnetic fields up to 20 Tesla. We observe a decrease in $G$ which goes up to about 15% in many Au contacts at 20 T. We perform calculations and find that pure Ag and Au do not present a strong field dependence of $G$, in agreement with previous results at smaller magnetic fields. We also find, however, that residual O$_2$ molecules attached close to the contact produce an an induced spin-polarized current, which leads to a decrease in $G$. We discuss the role of the magnetic response of the electrodes in the jump to contact. Our results suggest that single channel atomic size conductors with a sizeable response to a magnetic field can be built by combining noble metals and magnetically active molecular systems.

cond-mat.mes-hall↗