arXiv subjects

Samuel Kerschbaumer

Publications and source records attributed to Samuel Kerschbaumer.

3 recordsLinked to original sources

arXiv2026

Atomic scale demonstration of ferromagnetism in a single layer FeCl2 on Au(111)

FeCl2 is a promising single-layer material with sizeable magnetic susceptibility and insulating character that can be easily grown by molecular beam epitaxy on various surfaces. In order to include it into the select palette of van der Waals materials used to engineer functional heterostructures, it is necessary to confirm its magnetic and electronic ground states, and understand the influence of the supporting substrate. In this work, we unambiguously demonstrate ferromagnetic ordering in a single-layer FeCl2 on Au(111) by means of spin-polarized scanning tunnelling microscopy. The material features a relatively wide insulating gap of 3.3 eV and a strongly spin-polarized conduction band that emerges at 1.5 eV above the Fermi level. Atomic scale defects with triangular shape play a primary role in the electronic gap and spin density distribution. Specifically, in a region of 1.6 nm around each defect, the conduction band is locally suppressed and the tunnelling magneto-conductance is reduced a factor of four. By tracking the spin-dependent tunnelling conductance as a function of the applied magnetic field, we record atomically resolved hysteresis loops, revealing a soft ferromagnetic ground state with pronounced out-of-plane anisotropy and coercive fields in the range of 15-50 mT.

cond-mat.mtrl-sci↗

arXiv2025

Epitaxial growth of gold films on the elemental superconductors V(100), Nb(100) and Nb(110)

Quantum technologies require a new generation of superconducting electronic devices and circuitry. However, the superconducting materials used to construct them are restricted to a class of bulk superconductors. Gold films grown in contact with superconducting materials can exhibit superconducting correlations through the proximity effect, with various possible implementations in quantum technology. Here, we study the growth of flat Au films on various surfaces of the elemental superconductors vanadium and niobium through a combination of low-temperature scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). In particular, we investigate the growth morphology and composition as a function of temperature and coverage. We find that gold films can grow flat and oxygen-free when annealed to sufficiently high temperatures; however, they are also susceptible to partial intermixing with the substrate elements. Low-temperature scanning tunneling spectroscopy (STS) measurements elucidate the emergence of a proximitized superconducting gap at the gold surface. Additionally, we demonstrate the survival of the magnetic state of FeTPP-Cl molecules on the surface of these gold films, proving that they behave as a good support for probing molecular magnetism. We found that the exchange interaction between the molecular spin and the superconducting condensate can be inferred by the measurement of sub-gap Yu-Shiva-Rusinov states. Our work shows that proximitised Au films constitute a promising platform to explore on-superconducting-surface synthesis and the interaction between superconductivity and magnetism in a large spin-orbit coupling environment.

cond-mat.supr-con↗

arXiv2023

Superconducting Spintronic Heat Engine

Heat engines are key devices that convert thermal energy into usable energy. Strong thermoelectricity, at the basis of electrical heat engines, is present in superconducting spin tunnel barriers at cryogenic temperatures where conventional semiconducting or metallic technologies cease to work. Here we realize a superconducting spintronic heat engine consisting of a ferromagnetic insulator/superconductor/insulator/ferromagnet tunnel junction (EuS/Al/AlO$_x$/Co). The efficiency of the engine is quantified for bath temperatures ranging from 25 mK up to 800 mK, and at different load resistances. Moreover, we show that the sign of the generated thermoelectric voltage can be inverted according to the parallel or anti-parallel orientation of the two ferromagnetic layers, EuS and Co. This realizes a thermoelectric spin valve controlling the sign and strength of the Seebeck coefficient, thereby implementing a thermoelectric memory cell. We propose a theoretical model that allows describing the experimental data and predicts the engine efficiency for different device parameters.

cond-mat.mes-hall↗