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This is thethird volumeof the FAIRmat newsletter, which is published every six months. The FAIRmat newsletter includes project updates and recent milestones, introduction and opinion articles on topics in research data management and data infrastructures and insights into our community, including both our staff and users of our software and services. For those already involved in the project, the newsletter provides an update on what is happening in our different Tasks or working groups. For those new to FAIRmat, it offers current insight into the project’s goals, team and methods.

The discovery of the electrons' chiral induced spin selective transmission (CISS) through chiral molecules has opened the pathway for manipulating spin transport in nonmagnetic structures on the nanoscale. CISS has predominantly been explored in structurally helical molecules on surfaces, where the spin selectivity affects only the spin polarization of the electrons along their direction of propagation. Here, we demonstrate a spin selective electron transmission for the point-chiral molecule 3-methylcyclohexanone (3-MCHO) adsorbed on the chiral Cu(643)

Golden Vogel spirals, as deterministic aperiodic structures, support isotropic photonic band gaps and have inter-esting applications. Localized modes, such as band-edge states, are essential for tailored light-matter interaction. Here we report imaging of such modes using photoemission electron microscopy (PEEM). Tunable ultrashort light pulses excite them in golden Vogel spirals that were fabricated by focused-ion-beam (FIB) milling of an a-Si:H layer. The local near-field leads to electron emission, which is detected spatially resolved. The demonstration of FIB-textured a-Si:H as photonic material and the ability of mode imaging by PEEM offers means to spatiotemporally resolve mode dynamics and to perform nanospectroscopy. (c) 2023 Optica Publishing Group

We design and experimentally demonstrate an optical switch based on the interference of plasmonic modes in whispering gallery mode (WGM) antennas. Simultaneous excitation of even and odd WGM modes, enabled by a small symmetry breaking via non-normal illumination, allows switching the plasmonic near field between opposite sides of the antenna, depending on the excitation wavelength used in a wavelength range of 60 nm centered around 790 nm. This proposed switching mechanism is experimentally demonstrated by combining photoemission electron microscopy (PEEM) with a tunable wavelength femtosecond laser source in the visible and infrared.

We demonstrate the tuneablity of the ultrafast energy flow in magnetic/non-magnetic bilayer structures by changing the wavelength of the optical excitation. This is achieved by an advanced description of the temperature based $\mu$T-model that explicitly considers the wavelength- and layer-dependent absorption profile within multilayer structures. For the exemplary case of a Ni/Au bilayer, our simulations predict that the energy flow from Ni to Au is reversed when changing the wavelength of the excitation from the infrared to the ultraviolet spectral range. These predictions are fully supported by characteristic signatures in the magneto-optical Kerr traces of the Ni/Au model system. Our results will open up new avenues to steer and control the energy transport in designed magnetic multilayer for ultrafast spintronic applications., Comment: 6 pages (+3 pages supplemental), 5 figures (+1 figure in supplemental)

Controlling the structure formation of molecules on surfaces is fundamental for creating molecular nanostructures with tailored properties and functionalities and relies on tuning the subtle balance between intermolecular and molecule-surface interactions. So far, however, reliable rules of design are largely lacking, preventing the controlled fabrication of self-assembled functional structures on surfaces. In addition, while so far many studies focused on varying the molecular building blocks, the impact of systematically adjusting the underlying substrate has been less frequently addressed. Here, we elucidate the potential of tailoring the mesoscopic island shape by tuning the interactions at the molecular level. As a model system, we have selected the molecule dimolybdenum tetraacetate on three prototypical surfaces, Cu(111), Au(111) and CaF2(111). While providing the same hexagonal geometry, compared to Cu(111), the lattice constants of Au(111) and CaF2(111) differ by a factor of 1.1 and 1.5, respectively. Our high-resolution scanning probe microscopy images reveal molecular-level information on the resulting islands and elucidate the molecular-level design principles for the observed mesoscopic island shapes. Our study demonstrates the capability to tailor the mesoscopic island shape by exclusively tuning the substrate lattice constant, in spite of the very different electronic structure of the substrates involved. This work provides insights for developing general design strategies for controlling molecular mesostructures on surfaces.

We unravel the underlying near-field mechanism of the enhancement of the magneto-optical activity of bismuth-substituted yttrium iron garnet films (Bi:YIG) loaded with gold nanoparticles. The experimental results show that the embedded gold nanoparticles lead to a broadband enhancement of the magneto-optical activity with respect to the activity of the bare Bi:YIG films. Full vectorial near- and far-field simulations demonstrate that this broadband enhancement is the result of a magneto-optically enabled cross-talking of orthogonal localized plasmon resonances. Our results pave the way to the on-demand design of the magneto-optical properties of hybrid magneto-plasmonic circuitry., This work is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – TRR 173 – 268565370. E. Th. P. and S. D. P. acknowledge the Carl Zeiss Foundation. Ken-ichi Uchida (NIMS, Japan) is acknowledged for providing the Bi:YIG/AuNPs samples. Dipl.-Phys. Marc Vogel – AG von Freymann – TU Kaiserslautern is acknowledged for the introduction to CST software and his help with the installation of the package.

Photoemission orbital tomography (POT) allows for the complete characterization of the electronic and structural properties of well-ordered molecular films. We present femtosecond time-resolved POT data, allowing to image the ultrafast energy conversion in C60 through three different excitonic states.

In recent years, superconducting radio-frequency (SRF) cavities have been considered as candidates for qubits in quantum computing, showing longer photon lifetimes and, therefore, longer decoherence times of a cavity stored qubit compared to many other realizations. In modern particle accelerators, SRF cavities are the workhorse. Continuous research and development efforts are being undertaken to improve their properties, i.e., to increase the accelerating field and lower the surface resistance, which in turn increase the energy reach and duty cycle of accelerators. While some experimental milestones have been achieved, the mechanisms behind the still observed losses remain not fully understood. In this contribution we are going to show that a recently reported temperature treatment of Nb SRF cavities in the temperature range of 573–673 K, which reduces the residual surface resistance to unprecedented values, is linked to a reorganization of the niobium oxide and near-surface vacancy structure and that this reorganization can explain the observed improved performance in both applications, quantum computing and SRF cavities.

The prosperity and lifestyle of our society are very much governed by achievements in condensed matter physics, chemistry and materials science, because new products for sectors such as energy, the environment, health, mobility and information technology (IT) rely largely on improved or even new materials. Examples include solid-state lighting, touchscreens, batteries, implants, drug delivery and many more. The enormous amount of research data produced every day in these fields represents a gold mine of the twenty-first century. This gold mine is, however, of little value if these data are not comprehensively characterized and made available. How can we refine this feedstock; that is, turn data into knowledge and value? For this, a FAIR (findable, accessible, interoperable and reusable) data infrastructure is a must. Only then can data be readily shared and explored using data analytics and artificial intelligence (AI) methods. Making data 'findable and AI ready' (a forward-looking interpretation of the acronym) will change the way in which science is carried out today. In this Perspective, we discuss how we can prepare to make this happen for the field of materials science.

Understanding the differences between photon-induced and plasmon-induced hot electrons is essential for the construction of devices for plasmonic energy conversion. The mechanism of the plasmonic enhancement in photochemistry, photocatalysis, and light-harvesting and especially the role of hot carriers is still heavily discussed. The question remains, if plasmon-induced and photon-induced hot carriers are fundamentally different or if plasmonic enhancement is only an effect of field concentration producing these carriers in greater numbers. For the bulk plasmon resonance, a fundamental difference is known, yet for the technologically important surface plasmons, this is far from being settled. The direct imaging of surface plasmon-induced hot carriers could provide essential insight, but the separation of the influence of driving laser, field-enhancement, and fundamental plasmon decay has proven to be difficult. Here, we present an approach using a two-color femtosecond pump-probe scheme in time-resolved 2-photon-photoemission (tr-2PPE), supported by a theoretical analysis of the light and plasmon energy flow. We separate the energy and momentum distribution of the plasmon-induced hot electrons from that of photoexcited electrons by following the spatial evolution of photoemitted electrons with energy-resolved photoemission electron microscopy (PEEM) and momentum microscopy during the propagation of a surface plasmon polariton (SPP) pulse along a gold surface. With this scheme, we realize a direct experimental access to plasmon-induced hot electrons. We find a plasmonic enhancement toward high excitation energies and small in-plane momenta, which suggests a fundamentally different mechanism of hot electron generation, as previously unknown for surface plasmons.

Controlling the quantum confinement of (spin-dependent) electronic states by material design opens a unique avenue to accelerate the implementation of quantum technology in next generation photonic and spintronic applications. In the nanoworld, two-dimensional porous molecular networks have emerged as highly tunable material platform for the realization of exotic quantum phases for which the nanopores can be tuned by chemical functionalization of the size and shape of the molecules. Here, we demonstrate a new approach to control the periodicity, size, and barrier width in 2D porous molecular networks on surface by tuning the balance between intermolecular and molecule–surface interactions using temperature. At 106 K, the prototypical TPT molecules form nanoporous networks with different periodicity and barrier width depending on the surface reactivity. The network structures continuously transform into a close-packed molecular structure at room temperature. This reversible structural phase transition can ...

Organic photovoltaic devices operate by absorbing light and generating current. These two processes are governed by the optical and transport properties of the organic semiconductor. Despite their common microscopic origin—the electronic structure—disclosing their dynamical interplay is far from trivial. Here we address this issue by time-resolved photoemission to directly investigate the correlation between the optical and transport response in organic materials. We reveal that optical generation of non-interacting excitons in a fullerene film results in a substantial redistribution of all transport levels (within 0.4 eV) of the non-excited molecules. As all observed dynamics evolve on identical timescales, we conclude that optical and transport properties are completely interlinked. This finding paves the way for developing novel concepts for transport level engineering on ultrafast time scales that could lead to novel functional optoelectronic devices., Correlating the optoelectronic properties in organic semiconductors is vital to realizing devices with high performance and new functionalities. Here, the authors report the role of optically excited charge transfer excitons on energy level alignment of the transport levels in organic thin films.

The strength of light–matter interaction in condensed matter is fundamentally linked to the orientation and oscillation strength of the materials’ optical transition dipoles. Structurally anisotropic materials, e.g., elongated molecules, exhibit optical transition dipoles with fixed orientations that govern the angular-dependent light–matter interaction. Contrary, free electron-like metals should exhibit isotropic light–matter interaction with the light fields dictating the orientation of the optical transition dipoles. Here, we demonstrate that an anisotropic direction of the optical transition dipoles even exists in highly free electron-like noble metal surfaces. Our time- and phase-resolved photoemission experiment reveals coherent interference effects on the (110)-oriented silver surface after optical excitation with two non-interfering cross-polarized pulses. We explain this coherent material response within the density matrix formalism by an intrinsic coupling of the non-interfering light fields mediated by optical transition dipoles with fixed orientations in silver.

Surface plasmon polaritons carrying orbital angular momentum are of great fundamental and applied interest. However, common approaches for their generation are restricted to having a weak dependence on the properties of the plasmon-generating illumination, providing a limited degree of control over the amount of delivered orbital angular momentum. Here we experimentally show that by tailoring local and global geometries of vortex generators, a change in circular polarization handedness of light imposes arbitrary large switching in the delivered plasmonic angular momentum. Using time-resolved photoemission electron microscopy we demonstrate pristine control over the generation and rotation direction of high-order plasmonic vortices. We generalize our approach to create complex topological fields and exemplify it by studying and controlling a "bright vortex", exhibiting the breakdown of a high-order vortex into a mosaic of unity-order vortices while maintaining the overall angular momentum density. Our results provide tools for plasmonic manipulation and could be utilized in lab-on-a-chip devices.

Phase transitions between different aggregate states are omnipresent in nature and technology. Conventionally, a crystalline phase melts upon heating as we use ice to cool a drink. Already in 1903, Gustav Tammann speculated about the opposite process, namely melting upon cooling. So far, evidence for such “inverse” transitions in real materials is rare and limited to few systems or extreme conditions. Here, we demonstrate an inverse phase transition for molecules adsorbed on a surface. Molybdenum tetraacetate on copper(111) forms an ordered structure at room temperature, which dissolves upon cooling. This transition is mediated by molecules becoming mobile, i.e., by mobilization upon cooling. This unexpected phenomenon is ascribed to the larger number of internal degrees of freedom in the ordered phase compared to the mobile phase at low temperatures., We all know that ice becomes liquid upon heating. In contrast, melting upon cooling is an unusual behavior. A system of molecules adsorbed to a surface, which become mobile upon cooling, was developed. The key for understanding these counterintuitive phase transitions lies in the fact that the high temperature ordered phase possesses more degrees of freedom leading to a larger entropy than the low‐temperature unordered phase.

Phasenübergänge zwischen unterschiedlichen Aggregatzuständen sind in Natur und Technik allgegenwärtig. Üblicherweise schmilzt ein Kristall, wenn er erwärmt wird. Daher nutzen wir Eis, um einen Drink zu kühlen. Bereits im Jahre 1903 spekulierte Gustav Tammann über den umgekehrten Prozess des Schmelzens durch Kühlen. Bisher gibt es allerdings nur sehr wenige Beispiele für solche “inversen” Phasenübergänge, die meist auch auf extreme Bedingungen beschränkt sind. Hier zeigen wir einen inversen Phasenübergang von adsorbierten Molekülen auf einer Oberfläche. Molybdänacetat bildet bei Zimmertemperatur eine geordnete Struktur auf der (111)-Oberfläche von Kupfer, die sich beim Kühlen auflöst. Dieser Übergang entsteht dadurch, dass die Moleküle mobil werden, d. h., wir beobachten die Mobilisierung durch Kühlen. Dieses unerwartete Phänomen kann durch die große Zahl an internen Freiheitsgraden der geordneten Phase im Vergleich zur mobilen Phase erklärt werden.

One of the most important functionalities of the atomically thin insulator hexagonal boron nitride (hBN) is its ability to chemically and electronically decouple functional materials from highly reactive surfaces. It is therefore of utmost importance to uncover its structural properties on surfaces on an atomic and mesoscopic length scale. In this paper, we quantify the relative coverages of structurally different domains of a hBN layer on the Ni(111) surface using low-energy electron microscopy and the normal incidence x-ray standing wave technique. We find that hBN nucleates on defect sites of the Ni(111) surface and predominantly grows in two epitaxial domains that are rotated by ${60}^{\ensuremath{\circ}}$ with respect to each other. The two domains reveal identical adsorption heights, indicating a similar chemical interaction strength with the Ni(111) surface. The different azimuthal orientations of these domains originate from different adsorption sites of N and B. We demonstrate that the majority ($\ensuremath{\approx}70%$) of hBN domains exhibit a $(\mathrm{N},\mathrm{B})=(\mathrm{top},\mathrm{fcc})$ adsorption site configuration while the minority ($\ensuremath{\approx}30%$) show a $(\mathrm{N},\mathrm{B})=(\mathrm{top},\mathrm{hcp})$ configuration. Our study hence underlines the crucial role of the atomic adsorption configuration in the mesoscopic domain structures of in situ fabricated two-dimensional materials on highly reactive surfaces.

Surface alloys are a highly flexible class of low dimensional materials with the opportunity to tune and control the spin and charge carrier functionalities on the nanoscale. Here, we focus on the atomic and mesoscopic structural details of three distinct binary rare-earth-noble metals (NM) surface alloys by employing scanning tunneling microscopy and low energy electron diffraction. Using Dysprosium as the guest element on fcc(111) NM substrates, we identify the formation of non-commensurate surface alloy superstructures, which lead to homogeneous moiré patterns for DyCu2/Cu(111) and DyAu2/Au(111), while an inhomogeneous one is found for DyAg2/Ag(111). The local structure was analyzed for these samples and the observed differences are discussed in the light of the lattice mismatches of the alloy layer with respect to the underlying substrate. For the particularly intriguing case of a DyAg2 surface alloy, the surface alloy layer does not show a uniform long-range periodic structure, but consists of local hexagonal tiles separated by extended domain walls, which occur likely to relieve the in-plane strain within the DyAg2 surface alloy layer. Our findings clearly demonstrate that surface alloying is an intriguing tool to tailor the local atomic structure as well as the mesoscopic moiré structures of metallic heterostructures.

We investigated the surface and bulk properties of the pristine (110) surface of silver using threshold photoemission by excitation with light of 5.9 eV. Using a momentum microscope, we identified two distinct transitions along the $\overline{\mathrm{\ensuremath{\Gamma}}}\overline{\mathrm{Y}}$ direction of the crystal. The first one is a so far unknown surface resonance of the (110) noble-metal surface, exhibiting an exceptionally large bulk character that has so far been elusive in surface sensitive experiments. The second one stems from the well-known bulklike Mahan cone oriented along the $\mathrm{\ensuremath{\Gamma}}L$ direction inside the crystal but projected onto the (110)-surface cut. The existence of the new state is confirmed by photocurrent calculations, and its character is analyzed.

Understanding the differences between photon-induced and plasmon-induced hot electrons is essential for the construction of devices for plasmonic energy conversion. The mechanism of the plasmonic enhancement in photochemistry, photocatalysis, and light-harvesting and especially the role of hot carriers is still heavily discussed. The question remains, if plasmon-induced and photon-induced hot carriers are fundamentally different, or if plasmonic enhancement is only an effect of field concentration producing these carriers in greater numbers. For the bulk plasmon resonance, a fundamental difference is known, yet for the technologically important surface plasmons this is far from being settled. The direct imaging of surface plasmon-induced hot carriers could provide essential insight, but the separation of the influence of driving laser, field-enhancement, and fundamental plasmon decay has proven to be difficult. Here, we present an approach using a two-color femtosecond pump-probe scheme in time-resolved 2-photon-photoemission (tr-2PPE), supported by a theoretical analysis of the light and plasmon energy flow. We separate the energy and momentum distribution of the plasmon-induced hot electrons from the one of photoexcited electrons by following the spatial evolution of photoemitted electrons with energy-resolved Photoemission Electron Microscopy (PEEM) and Momentum Microscopy during the propagation of a Surface Plasmon Polariton (SPP) pulse along a gold surface. With this scheme, we realize a direct experimental access to plasmon-induced hot electrons. We find a plasmonic enhancement towards high excitation energies and small in-plane momenta, which suggests a fundamentally different mechanism of hot electron generation, as previously unknown for surface plasmons.

Controlling self-assembled nanostructures on bulk insulators at room temperature is crucial towards the fabrication of future molecular devices, e.g., in the field of nanoelectronics, catalysis and sensor applications. However, at temperatures realistic for operation anchoring individual molecules on electrically insulating support surfaces remains a big challenge. Here, we present the formation of an ordered array of single anchored molecules, dimolybdenum tetraacetate, on the (10.4) plane of calcite (CaCO3). Based on our combined study of atomic force microscopy measurements and density functional theory calculations, we show that the molecules neither diffuse nor rotate at room temperature. The strong anchoring is explained by electrostatic interaction of an ideally size-matched molecule. Especially at high coverage, a hard-sphere repulsion of the molecules and the confinement at the calcite surface drives the molecules to form locally ordered arrays, which is conceptually different from attractive linkers as used in metal-organic frameworks. Our work demonstrates that tailoring the molecule-surface interaction opens up the possibility for anchoring individual metal-complexing molecules into ordered arrays., Arrays of ordered metal atoms on bulk insulating materials are promising for future applications, such as optoelectronics and data storage. Here, the authors demonstrate a strategy to create an ordered metal array based on tailored anchoring and hard-sphere repulsion of metal-complexing molecules.

The high flexibility of organic molecules offers great potential for designing the optical properties of optically active materials for the next generation of optoelectronic and photonic applications. However, despite successful implementations of molecular materials in today’s display and photovoltaic technology, many fundamental aspects of the light-to-charge conversion in molecular materials have still to be uncovered. Here, we focus on the ultrafast dynamics of optically excited excitons in C60 thin films depending on the molecular coverage and the light polarization of the optical excitation. Using time- and momentum-resolved photoemission with femtosecond extreme ultraviolet (fs-XUV) radiation, we follow the exciton dynamics in the excited states while simultaneously monitoring the signatures of the excitonic charge character in the renormalization of the molecular valence band structure. Optical excitation with visible light results in the instantaneous formation of charge-transfer (CT) excitons, which transform stepwise into Frenkel-like excitons at lower energies. The number and energetic position of the CT and Frenkel-like excitons within this cascade process are independent of the molecular coverage and the light polarization of the optical excitation. In contrast, the depopulation times of the CT and Frenkel-like excitons depend on the molecular coverage, while the excitation efficiency of CT excitons is determined by the light polarization. Our comprehensive study reveals the crucial role of CT excitons for the excited-state dynamics of homomolecular fullerene materials and thin films.

Molecular materials enable a vast variety of functionalities for novel electronic and spintronic devices. The unique possibility to alter organic molecules or metallic substrates offers the opportunity to optimize interfacial properties for almost any desired field of application. For this reason, we extend the successful approach to control metal-organic interfaces by surface alloying. We present a comprehensive characterization of the structural and electronic properties of the interface formed between the prototypical molecule PTCDA and a Sn-Ag surface alloy grown on an Ag(111) single crystal surface. We monitor the changes of adsorption height of the surface alloy atoms and electronic valence band structure upon adsorption of one layer of PTCDA using the normal incidence x-ray standing wave technique in combination with momentum-resolved photoelectron spectroscopy. We find that the vertical buckling and the surface band structure of the $\mathrm{Sn}{\mathrm{Ag}}_{2}$ surface alloy is not altered by the adsorption of one layer of PTCDA, in contrast to our recent study of PTCDA on a $\mathrm{Pb}{\mathrm{Ag}}_{2}$ surface alloy [B. Stadtm\"uller et al., Phys. Rev. Lett. 117, 096805 (2016)]. In addition, the vertical adsorption geometry of PTCDA and the interfacial energy level alignment indicate the absence of any chemical interaction between the molecule and the surface alloy. We attribute the different interactions at these PTCDA/surface alloy interfaces to the presence or absence of local $\ensuremath{\sigma}$-bonds between the PTCDA oxygen atoms and the surface atoms. Combining our findings with results from literature, we are able to propose an empiric rule for engineering the surface band structure of alloys by adsorption of organic molecules.

Optically induced spin transfer (OISTR) is a pathway to control magnetization dynamics in complex materials on femto- to attosecond timescales. The direct interaction of the laser field with the material creates transient nonequilibrium states, which can exhibit an efficient spin transfer between different magnetic subsystems. How far this spin manipulation via OISTR is a general phenomenon or restricted to a subset of materials with specific properties is an open experimental and theoretical question. Using time-resolved magneto-optical Kerr measurements and time-dependent density functional theory we investigate OISTR in Heusler compounds. We show that the half-Heusler materials NiMnSb and CoMnSb exhibit strong signatures of OISTR, whereas this is less pronounced in the full-Heusler compounds Co2MnSi, Co2FeSi, and Co2FeAl in agreement with ab initio calculations. Our work opens up a systematic path for coherent manipulation of spin dynamics by direct light-matter interaction.

Transport phenomena in molecular materials are intrinsically linked to the orbital character and the degree of localization of the valence states. Here we combine angle-resolved photoemission with photoemission tomography to determine the spatial distribution of all molecular states of the valence band structure of a ${\mathrm{C}}_{60}$ thin film. While the two most frontier valence states exhibit a strong band dispersion, the states at larger binding energies are characterized by distinct emission patterns in energy and momentum space. Our findings demonstrate the formation of an atomic crystal-like band structure in a molecular solid with delocalized $\ensuremath{\pi}$-like valence states and strongly localized $\ensuremath{\sigma}$ states at larger binding energies.

We compare the decay of plasmons and "conventional" hot electrons within the same series of gold/metal oxide interfaces. We found an accelerated decay of hot electrons at gold-metal oxide interfaces with decreasing band gap of the oxide material. The decay is accelerated by the increased phase space for electron scattering caused by additional interfacial states. Since plasmons decay faster within the same series of gold-metal oxide interfaces, we propose plasmons are able to decay into the same interfacial states as hot electrons. The similarity of plasmon damping to conventional hot electron decay implies that many classical surface analysis techniques and theoretical concepts are transferable to plasmonic systems. Our results support the mechanism of direct decay of plasmons into interfacial hot electron pairs but the utility of these interfacial states for charge transfer reactions remains to be investigated.

We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) to investigate ultrafast charge transfer in an epitaxial heterostructure made of monolayer WS$_2$ and graphene. This heterostructure combines the benefits of a direct gap semiconductor with strong spin-orbit coupling and strong light-matter interaction with those of a semimetal hosting massless carriers with extremely high mobility and long spin lifetimes. We find that, after photoexcitation at resonance to the A-exciton in WS$_2$, the photoexcited holes rapidly transfer into the graphene layer while the photoexcited electrons remain in the WS$_2$ layer. The resulting charge transfer state is found to have a lifetime of $\sim1$\,ps. We attribute our findings to differences in scattering phase space caused by the relative alignment of WS$_2$ and graphene bands as revealed by high resolution ARPES. In combination with spin-selective excitation using circularly polarized light the investigated WS$_2$/graphene heterostructure might provide a new platform for efficient optical spin injection into graphene., 28 pages, 14 figures