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Spin–orbit coupling (SOC) is a fundamental physical interaction, which describes how the electrons’ spin couples to their orbital motion. It is the source of a vast variety of fascinating phenomena in nanostructures. Although in most theoretical descriptions of high-temperature superconductivity SOC has been neglected, including this interaction can, in principle, revise the microscopic picture. Here by preforming energy-, momentum-, and spin-resolved spectroscopy experiments we demonstrate that while probing the dynamic charge response of the FeSe monolayer on strontium titanate, a prototype two-dimensional high-temperature superconductor using electrons, the scattering cross-section is spin dependent. We unravel the origin of the observed phenomenon and show that SOC in this two-dimensional superconductor is strong. We anticipate that such a strong SOC can have several consequences on the electronic structures and may compete with other pairing scenarios and be crucial for the mechanism of superconductivity.

Interest in electroluminescence of single molecules is stimulated by the prospect of possible applications in novel light emitting devices. Recent studies provide valuable insights into the mechanisms leading to single molecule electroluminescence. Concrete information on how to boost the intensity of the emitted light, however, is rare. By combining scanning tunnelling microscopy (STM) and quantum chemical calculations, we show that the light emission efficiencies of an individual hydrogen-phthalocyanine molecule can be increased by a factor of ≈19 upon charging. This boost in intensity can be explained by the development of a vertical dipole moment normal to the substrate facilitating out-coupling of the local excitation to the far field. As this effect is not related to the specific nature of hydrogen-phthalocyanine, it opens up a general way to increase light emission from molecular junctions.

One promising route toward encoding information is to utilize the two stable electronic states of a spin crossover molecule. Although this property is clearly manifested in transport across single molecule junctions, evidence linking charge transport across a solid-state device to the molecular film’s spin state has thus far remained indirect. To establish this link, we deploy materials-centric and device-centric operando experiments involving X-ray absorption spectroscopy. We find a correlation between the temperature dependencies of the junction resistance and the Fe spin state within the device’s [Fe(H2B(pz)2)2(NH2-phen)] molecular film. We also factually observe that the Fe molecular site mediates charge transport. Our dual operando studies reveal that transport involves a subset of molecules within an electronically heterogeneous spin crossover film. Our work confers an insight that substantially improves the state-of-the-art regarding spin crossover-based devices, thanks to a methodology that can benefit device studies of other next-generation molecular compounds.

Magnetic molecules have the potential to be used as building blocks for bits in quantum computers. The spin states of the magnetic ion in the molecule can be represented by the effective spin Hamiltonian describing the zero field splitting (ZFS) of the magnetic states. We determined the ZFS of mechanically flexible metal-chelate molecules (Co, Ni, and Cu as metal ions) adsorbed on Cu2N/Cu(100) by inelastic tunneling spectroscopy at temperatures down to 30 mK. When moving the tip toward the molecule, the tunneling current abruptly jumps to higher values, indicating the sudden deformation of the molecule bridging the tunneling junction. Hand in hand with the formation of the contact, an abrupt change of the ZFS occurs. This work also implies that ZFS expected in mechanical break junctions can drastically deviate from that of adsorbed molecules probed by other techniques.

Das Rastertunnelmikroskop bildet mit seiner Spitze Oberflächen und Nanostrukturen mit atomarer Präzision ab. Traditionell klärt es die Gleichgewichtseigenschaften von Atomen, Elektronen und magnetischen Dipolen auf. Inzwischen kann es auch dynamische Nichtgleichgewichts‐Eigenschaften mit atomarer Präzision vermessen. Drei Beispiele demonstrieren dies. Im ersten Beispiel werden mit der inelastischen Tunnelspektroskopie die Energien und Lebensdauern von magnetischen Anregungen, Magnonen, vermessen. Im zweiten Beispiel bringt eine oszillierende Tunnelspannung eine Nanotrommel aus nur 800 Kohlenstoffatomen zum Schwingen. Im dritten Beispiel wird das Umklappen des magnetischen Dipols eines Atoms mit Nanosekunden‐Präzision verfolgt. Dabei zeigt sich, dass der Dipol seine magnetische Ausrichtung nicht durch Drehen, sondern durch Tunneln ändert.

We present an overview of the technique of spin-polarized scanning tunneling microscopy (Sp-STM) and its application to high-resolution magnetic imaging. In STM, the electron density near the sample surface is imaged. Additionally, Sp-STM allows a mapping of the spin polarization of the electronic density, which is related to the magnetic configuration of the sample. Two primary imaging modes of Sp-STM are currently in use: the spectroscopic mode and the differential magnetic mode. The principles of the two modes are explained in the framework of imaging ferromagnetic nanostructures and antiferromagnetic surfaces. The advantages and drawbacks of the two approaches are discussed, and the strength of Sp-STM to map even complex spin structures on the nanometer scale is illustrated.

Magnetoelectric coupling at metal surfaces opens up a new possibility for metallic nonvolatile magnetic data-storage devices, in which the magnetic bits are controlled by an electric field. We studied the atomic and magnetic order in bilayer Fe nano-islands grown on a Cu(111) substrate with a scanning tunneling microscopy setup in ultra high vacuum at 4.5 K. Electric field pulses ($10^{8}$--$10^{9}$ V/m) were found to be able to cause a displacement of the Fe atoms, switching simultaneously the crystalline and the magnetic order, which is the prove of magnetoelectric coupling at the metallic Fe surface. We also succeeded in controlling the direction of the switching by the polarity of the electric field.

The control of atomically flat interfaces between iron (Fe) and insulating oxide films, such as the Fe/MgO(001) interface, is crucial for tunnel-magnetoresistance (TMR) devices. However, the realization of an ideal atomically flat and clean interface is rather difficult since iron easily binds to impurities such as oxygen. Atomic step defects and iron oxide at the interface could reduce TMR. In this study, the oxidization of an atomically flat and clean Fe(001)-whisker single crystal at different substrate and annealing temperatures was investigated with an ultrahigh-vacuum scanning tunneling microscope (STM). Annealing up to a temperature of 850 K was required to obtain ordered and atomically flat Fe(001)-p(1x1)O terraces after the oxidization with the coexistence of Fe-O nanoislands ([?]1 nm in height, [?]50 nm in size). We found that the growth of such nanoislands, which enhances interface roughness, strongly depends on the substrate temperature (T S) during the oxidization. A T S lower than 300 K reduces the coverage by the nanoislands to less than 10%.