2026
|
| 6. | C. S. Kern, X Yang, G. Zamborlini, S. Mearini, M. Jugovac, V. Feyer, U. De Giovannini, A. Rubio, S. Soubatch, M. G. Ramsey F. S. Tautz, P. Puschnig Circular dichroism in the photoelectron angular distribution of achiral molecules Journal Article In: Phys. Rev. Research, vol. 8, iss. 023275, 2026. @article{Kern2026,
title = {Circular dichroism in the photoelectron angular distribution of achiral molecules},
author = {C. S. Kern and X Yang and G. Zamborlini and S. Mearini and M. Jugovac and V. Feyer and U. De Giovannini and A. Rubio and S. Soubatch and M. G. Ramsey F. S. Tautz and P. Puschnig},
url = {https://journals.aps.org/prresearch/abstract/10.1103/6bkb-4rm3},
doi = {10.1103/6bkb-4rm3},
year = {2026},
date = {2026-06-11},
journal = {Phys. Rev. Research},
volume = {8},
issue = { 023275},
abstract = {Circular dichroism in the angular distribution (CDAD) is the effect that the angular intensity distribution of photoemitted electrons depends on the handedness of the incident circularly polarized light. The origin of CDAD can be manifold, including intrinsic properties of the system under study, such as chirality, spin-orbit interaction, or quantum-geometrical properties, but CDAD can also originate from final-state effects influenced by the experimental geometry. For example, CDAD has been reported for achiral organic molecules at the interface to metallic substrates. For this latter case, we investigate two prototypical 𝜋
-conjugated molecules, namely, tetracene and pentacene, whose frontier orbitals have a similar shape but exhibit distinctly different symmetries. By comparing experimental CDAD momentum maps with simulations within time-dependent density functional theory, we show how the final state of the photoelectron must be regarded as the source of the CDAD in such otherwise achiral and quantum-geometrically trivial systems. We gain additional insight into the mechanism by employing a simple scattering model for the final state, which allows us to decompose the CDAD signal into partial wave contributions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Circular dichroism in the angular distribution (CDAD) is the effect that the angular intensity distribution of photoemitted electrons depends on the handedness of the incident circularly polarized light. The origin of CDAD can be manifold, including intrinsic properties of the system under study, such as chirality, spin-orbit interaction, or quantum-geometrical properties, but CDAD can also originate from final-state effects influenced by the experimental geometry. For example, CDAD has been reported for achiral organic molecules at the interface to metallic substrates. For this latter case, we investigate two prototypical 𝜋
-conjugated molecules, namely, tetracene and pentacene, whose frontier orbitals have a similar shape but exhibit distinctly different symmetries. By comparing experimental CDAD momentum maps with simulations within time-dependent density functional theory, we show how the final state of the photoelectron must be regarded as the source of the CDAD in such otherwise achiral and quantum-geometrically trivial systems. We gain additional insight into the mechanism by employing a simple scattering model for the final state, which allows us to decompose the CDAD signal into partial wave contributions. |
| 5. | S. Mearini, F. Auer, M. Laßhofer, A. Windischbacher, D. Brandstetter, D. Baranowski, Y. Y. Grisan Qiu, I. Cojocariu, M. Jugovac, M. Sterrer, G. Zamborlini, V. Feyer, C. M. Schneider Single Ni Atoms Drive Carboxyl Deprotonation in Metal–Organic Chains Journal Article In: ACS Nano, vol. 20, iss. 16, pp. 12596–12603, 2026. @article{Mearini2026,
title = {Single Ni Atoms Drive Carboxyl Deprotonation in Metal–Organic Chains},
author = {S. Mearini and F. Auer and M. Laßhofer and A. Windischbacher and D. Brandstetter and D. Baranowski and Y. Y. Grisan Qiu and I. Cojocariu and M. Jugovac and M. Sterrer and G. Zamborlini and V. Feyer and C. M. Schneider},
url = {https://pubs.acs.org/doi/10.1021/acsnano.6c01444},
doi = {10.1021/acsnano.6c01444},
year = {2026},
date = {2026-04-17},
journal = {ACS Nano},
volume = {20},
issue = {16},
pages = {12596–12603},
abstract = {Understanding how charge transfer and ligand activation processes govern metal–organic coordination at surfaces is crucial for controlling on-surface synthesis and the formation of low-dimensional architectures. Here, we show that Ni promotes the deprotonation of the carboxyl groups of terephthalic acid (TPA) on Ag(100), leading to the formation of linear metal–organic coordination chains. Scanning tunneling microscopy reveals that these chains emerge from preassembled hydrogen-bonded TPA stripes. X-ray photoelectron spectroscopy identifies stabilization of the Ni centers in the Ni(I) oxidation state through a single-electron charge transfer process, accompanied by the formation of deprotonated carboxylate species. Valence band spectroscopy reveals a coordination-induced electronic reorganization between Ni and TPA through the emergence of hybrid states, in agreement with complementary theoretical modeling. Together, these findings identify charge-transfer-driven deprotonation as the central mechanism governing the formation of linear metal–organic chains.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Understanding how charge transfer and ligand activation processes govern metal–organic coordination at surfaces is crucial for controlling on-surface synthesis and the formation of low-dimensional architectures. Here, we show that Ni promotes the deprotonation of the carboxyl groups of terephthalic acid (TPA) on Ag(100), leading to the formation of linear metal–organic coordination chains. Scanning tunneling microscopy reveals that these chains emerge from preassembled hydrogen-bonded TPA stripes. X-ray photoelectron spectroscopy identifies stabilization of the Ni centers in the Ni(I) oxidation state through a single-electron charge transfer process, accompanied by the formation of deprotonated carboxylate species. Valence band spectroscopy reveals a coordination-induced electronic reorganization between Ni and TPA through the emergence of hybrid states, in agreement with complementary theoretical modeling. Together, these findings identify charge-transfer-driven deprotonation as the central mechanism governing the formation of linear metal–organic chains. |
| 4. | D. M. Janas, M. S. Arndt, J. E. Nitschke, L. Sternemann, V. Mischke, V. Feyer, I. Cojocariu, D. Baranowski, A. Sala, A. Windischbacher, P. Puschnig, J. Dreiser, S. Ponzoni, G. Zamborlini, M. Cinchetti Spin-Selective Interface Engineering in Oxide–Ferromagnetic Junctions via Atomic-Scale Oxygen Control Journal Article In: Advanced Science, vol. 13, iss. 25, no. e23165, 2026. @article{Janas2026,
title = {Spin-Selective Interface Engineering in Oxide–Ferromagnetic Junctions via Atomic-Scale Oxygen Control},
author = {D. M. Janas and M. S. Arndt and J. E. Nitschke and L. Sternemann and V. Mischke and V. Feyer and I. Cojocariu and D. Baranowski and A. Sala and A. Windischbacher and P. Puschnig and J. Dreiser and S. Ponzoni and G. Zamborlini and M. Cinchetti},
url = {https://advanced.onlinelibrary.wiley.com/doi/10.1002/advs.202523165},
doi = {10.1002/advs.202523165},
year = {2026},
date = {2026-02-20},
journal = {Advanced Science},
volume = {13},
number = {e23165},
issue = {25},
abstract = {Atomic-scale control of oxide–ferromagnet interfaces is crucial for optimizing spintronic heterostructures, yet interfacial oxygen remains difficult to control and verify. Here, we deterministically tune the prototypical MgO/Fe(100) interface from oxygen-free terminations to fully intercalated oxygen layers by reactive growth under controlled O2 exposure, while preserving epitaxy. Momentum-resolved photoemission identifies oxygen-dependent fingerprints in k-space that originate from the buried interface and persist up to a thickness of 8 layers of MgO. Insights from complementary spectroscopic methods link these k-space signatures to interfacial chemistry, structural order, work-function shifts, and an oxygen-induced interface resonance within the MgO gap that alters the tunneling response. The combined results define a calibrated growth protocol that allows reproducibly preparing and identifying three distinct terminations — oxygen-free, partially oxidized, and oxygen-intercalated — and enables post-growth conversion even in thicker films. Complementary spin-resolved experiments reveal that oxygen-free interfaces exhibit pronounced suppression of minority-spin spectral weight at the Fermi level, consistent with coherent spin filtering across crystalline MgO, whereas oxygen intercalation reduces the spin contrast at EF. By turning interfacial oxygen from an uncontrolled variable into a measurable, adjustable parameter, our approach establishes MgO/Fe(100) as a benchmark platform for optimizing spintronic functionality in oxide/metal junctions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Atomic-scale control of oxide–ferromagnet interfaces is crucial for optimizing spintronic heterostructures, yet interfacial oxygen remains difficult to control and verify. Here, we deterministically tune the prototypical MgO/Fe(100) interface from oxygen-free terminations to fully intercalated oxygen layers by reactive growth under controlled O2 exposure, while preserving epitaxy. Momentum-resolved photoemission identifies oxygen-dependent fingerprints in k-space that originate from the buried interface and persist up to a thickness of 8 layers of MgO. Insights from complementary spectroscopic methods link these k-space signatures to interfacial chemistry, structural order, work-function shifts, and an oxygen-induced interface resonance within the MgO gap that alters the tunneling response. The combined results define a calibrated growth protocol that allows reproducibly preparing and identifying three distinct terminations — oxygen-free, partially oxidized, and oxygen-intercalated — and enables post-growth conversion even in thicker films. Complementary spin-resolved experiments reveal that oxygen-free interfaces exhibit pronounced suppression of minority-spin spectral weight at the Fermi level, consistent with coherent spin filtering across crystalline MgO, whereas oxygen intercalation reduces the spin contrast at EF. By turning interfacial oxygen from an uncontrolled variable into a measurable, adjustable parameter, our approach establishes MgO/Fe(100) as a benchmark platform for optimizing spintronic functionality in oxide/metal junctions. |
2025
|
| 3. | C. S. Kern, X. Yang, G. Zamborlini, S. Mearini, M. Jugovac, V. Feyer, U. De Giovannini, A. Rubio, S. Soubatch, M. G. Ramsey, F. S. Tautz, P. Puschnig Circular dichroism in the photoelectron angular distribution of achiral molecules Journal Article Forthcoming In: arXiv:2507.12113 [cond-mat.mtrl-sci], Forthcoming. @article{Kern2025,
title = {Circular dichroism in the photoelectron angular distribution of achiral molecules},
author = {C. S. Kern and X. Yang and G. Zamborlini and S. Mearini and M. Jugovac and V. Feyer and U. De Giovannini and A. Rubio and S. Soubatch and M. G. Ramsey and F. S. Tautz and P. Puschnig},
url = {https://arxiv.org/abs/2507.12113},
doi = {10.48550/arXiv.2507.12113},
year = {2025},
date = {2025-07-16},
urldate = {2025-07-16},
journal = {arXiv:2507.12113 [cond-mat.mtrl-sci]},
keywords = {},
pubstate = {forthcoming},
tppubtype = {article}
}
|
| 2. | Y. Y. Grisan Qiu, D. Brandstetter, S. Mearini, D. Baranowski, I. Cojocariu, M. Jugovac, G. Zamborlini, P. Gargiani, M. Valvidares, A. Windischbacher, P. Puschnig, V. Feyer, C. M. Schneider Conformation-Driven Nickel Redox States and Magnetism in 2D Metal–organic Frameworks Journal Article In: Adv. Funct. Mater., vol. 2418186, 2025. @article{Qiu2025,
title = {Conformation-Driven Nickel Redox States and Magnetism in 2D Metal–organic Frameworks},
author = {Y. Y. Grisan Qiu and D. Brandstetter and S. Mearini and D. Baranowski and I. Cojocariu and M. Jugovac and G. Zamborlini and P. Gargiani and M. Valvidares and A. Windischbacher and P. Puschnig and V. Feyer and C. M. Schneider},
url = {https://advanced.onlinelibrary.wiley.com/doi/10.1002/adfm.202418186?af=R},
doi = {10.1002/adfm.202418186},
year = {2025},
date = {2025-01-29},
urldate = {2025-01-29},
journal = {Adv. Funct. Mater.},
volume = {2418186},
abstract = {2D metal–organic frameworks (2D MOFs) attract considerable attention because of their versatile properties and as potential candidates for single-atom catalysis, high-density information storage media or molecular electronics and spintronics devices. Their unique characteristics arise from an intricate interplay between the metal center, the surrounding ligands and the underlying substrate. Here, the intrinsic magnetic and electronic properties of a single-layer MOF on graphene is investigated with a combination of spectroscopic techniques and theoretical modeling. Taking advantage of the weak interaction between the MOF and graphene substrate, it is specifically focused on the influence of the coordination environment on these properties. Notably, two distinct coordination configurations are observed for the transition metal centers within the 2D MOF, and clarify how axial distortions in the ligand field affect the hybridization between the Ni 3d states and the π-symmetric molecular orbitals of 7,7,8,8-tetracyanoquinodimethane ligands, leading to the coexistence of two Ni redox states with different spin configurations. Furthermore, the transition from a nearly free-standing MOF is examined to metal-supported frameworks, elucidating the impact of substrate interactions on the electronic and magnetic properties. The findings advance the understanding of MOFs and offer insights into developing functional materials with tailored magnetic and electronic properties.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2D metal–organic frameworks (2D MOFs) attract considerable attention because of their versatile properties and as potential candidates for single-atom catalysis, high-density information storage media or molecular electronics and spintronics devices. Their unique characteristics arise from an intricate interplay between the metal center, the surrounding ligands and the underlying substrate. Here, the intrinsic magnetic and electronic properties of a single-layer MOF on graphene is investigated with a combination of spectroscopic techniques and theoretical modeling. Taking advantage of the weak interaction between the MOF and graphene substrate, it is specifically focused on the influence of the coordination environment on these properties. Notably, two distinct coordination configurations are observed for the transition metal centers within the 2D MOF, and clarify how axial distortions in the ligand field affect the hybridization between the Ni 3d states and the π-symmetric molecular orbitals of 7,7,8,8-tetracyanoquinodimethane ligands, leading to the coexistence of two Ni redox states with different spin configurations. Furthermore, the transition from a nearly free-standing MOF is examined to metal-supported frameworks, elucidating the impact of substrate interactions on the electronic and magnetic properties. The findings advance the understanding of MOFs and offer insights into developing functional materials with tailored magnetic and electronic properties. |
2022
|
| 1. | X. Yang, M. Jugovac, G. Zamborlini, V. Feyer, G. Koller, P. Puschnig, S. Soubatch, M. G. Ramsey, F. S. Tautz Momentum-selective orbital hybridisation Journal Article In: Nat. Commun., vol. 13, pp. 5148, 2022. @article{Yang2022,
title = {Momentum-selective orbital hybridisation},
author = {X. Yang and M. Jugovac and G. Zamborlini and V. Feyer and G. Koller and P. Puschnig and S. Soubatch and M. G. Ramsey and F. S. Tautz},
doi = {10.1038/s41467-022-32643-z},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {Nat. Commun.},
volume = {13},
pages = {5148},
abstract = {When a molecule interacts chemically with a metal surface, the orbitals of the molecule hybridise with metal states to form the new eigenstates of the coupled system. Spatial overlap and energy matching are determining parameters of the hybridisation. However, since every molecular orbital does not only have a characteristic spatial shape, but also a specific momentum distribution, one may additionally expect a momentum matching condition; after all, each hybridising wave function of the metal has a defined wave vector, too. Here, we report photoemission orbital tomography measurements of hybrid orbitals that emerge from molecular orbitals at a molecule-on-metal interface. We find that in the hybrid orbitals only those partial waves of the original orbital survive which match the metal band structure. Moreover, we find that the conversion of the metal’s surface state into a hybrid interface state is also governed by momentum matching constraints. Our experiments demonstrate the possibility to measure hybridisation momentum-selectively, thereby enabling deep insights into the complicated interplay of bulk states, surface states, and molecular orbitals in the formation of the electronic interface structure at molecule-on-metal hybrid interfaces.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
When a molecule interacts chemically with a metal surface, the orbitals of the molecule hybridise with metal states to form the new eigenstates of the coupled system. Spatial overlap and energy matching are determining parameters of the hybridisation. However, since every molecular orbital does not only have a characteristic spatial shape, but also a specific momentum distribution, one may additionally expect a momentum matching condition; after all, each hybridising wave function of the metal has a defined wave vector, too. Here, we report photoemission orbital tomography measurements of hybrid orbitals that emerge from molecular orbitals at a molecule-on-metal interface. We find that in the hybrid orbitals only those partial waves of the original orbital survive which match the metal band structure. Moreover, we find that the conversion of the metal’s surface state into a hybrid interface state is also governed by momentum matching constraints. Our experiments demonstrate the possibility to measure hybridisation momentum-selectively, thereby enabling deep insights into the complicated interplay of bulk states, surface states, and molecular orbitals in the formation of the electronic interface structure at molecule-on-metal hybrid interfaces. |
