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Phys. Rev. B 113, 035113

Optical control of a metastable phase in the charge density wave Mott insulator 1⁢𝑇−TaS2 investigated using time- and angle-resolved photoemission spectroscopy

T. Saha, A. Pramanik and R. Osama et al.

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T. Saha, A. Pramanik, R. Osama et al.

Light-induced metastable phases are exotic, long-lived out-of-equilibrium states of matter. Optical control offers a powerful approach to engineering these phases, enabling dynamic tuning of their electronic and structural properties. Using time- and angle-resolved photoemission spectroscopy, we investigate the emergence of a metastable phase induced by a strong infrared pump in the charge-density-wave (CDW)-Mott insulator 1⁢𝑇−TaS2. Furthermore, we demonstrate how its properties can be optically manipulated by varying the photoexcitation strength. A long-lived stabilization of the renormalized electronic band structure serves as a signature of the metastable phase. It displays a relaxed periodic lattice distortion (PLD) and primarily lattice-driven dynamics. The emergence of a new dispersive band in the vicinity of the Hubbard bands reveals the formation of a novel band structure unique to the metastable phase. Our pump-fluence-dependent studies reveal a threshold (incident) fluence 𝐹𝐶∼1.3⁢mJ/cm2 for inducing the metastable phase, above which the band renormalization continuously evolves with increasing fluence. For 𝐹⩽ 3.4 mJ/cm2, stronger photoexcitation progressively drives the phase to higher energies, accompanied by a more relaxed PLD and reduced CDW amplitude. The properties of the metastable phase are strongly influenced by the transient dynamics at each fluence, and the associated fast timescales suggest that the intrinsic CDW amplitude mode remains unaffected by optical manipulation. These findings highlight the potential of optical control in tuning the properties of metastable phases in quantum materials, offering new insights into the manipulation of CDW systems and paving the way for future investigations in nonequilibrium phase engineering.

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J Synchrotron Radiat. 2025 Oct 27; 32(Pt 6): 1396–1402

Ultra-thin (<2 µm) silicon carbide free-standing membranes as beam position monitors for soft and tender X-ray beamlines

E. Medina, G. Trovato and L. Calcagno et al.

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E. Medina, G. Trovato, L. Calcagno et al.

Conventional beam intensity monitor technologies, such as 'gold-meshes' and 'diamond conductive thin films', currently applied to tender and soft X-ray beams, encounter numerous application challenges, including diffraction effects, low signal strength, non-uniform transparency, and lack of position information. This study explores the potential of very thin (< 2 mu m) silicon carbide freestanding membranes, as in-line, minimally interfering beam intensity and position monitors, with high-lateral resolution, for soft and tender X-ray beamlines. Initial experimental assessments were conducted at the NanoMAX beamline at MAX IV to analyze the performance of such very thin devices in monitoring tightly focused (< 1 mu m FWHM) beams. The tests revealed that employing fourquadrant sensor layouts on such thin sensors resulted in significant charge collection losses in the regions between the quadrants and, under high electric field conditions, in charge multiplication effects (avalanche effects). Through Sentaurus TCAD theoretical simulations, the limitations of the four-quadrant design for such applications and the potential of an alternative technology (resistive X-ray beam postion monitor) were clarified.

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Chemistry – A European Journal (2025): e02828

Spectroscopic Fingerprinting of Coordination‐driven Spin States in Metal‐organic Architectures

Y. Y. G. Qiu, S. Carlotto, S. Mearini and et al.

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Y. Y. G. Qiu, S. Carlotto, S. Mearini, et al.

Determining the local geometry of metal-organic architecture on substrates is challenging, as substrate interactions can alter the metal coordination relative to the free-standing structure. Here, combining density functional theory (DFT) and restricted open-shell configuration interaction with singles (ROCIS) calculations on isolated cobalt-7,7,8,8-tetracyanoquinodimethane (Co-TCNQ) complexes, together with X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD), directly reveals the coordination motifs of Co centers in a 2D Co-TCNQ framework on graphene. The calculated Co L3,2-edges spectroscopic fingerprints for nearly planar (Co2+, S = 1/2) and distorted tetrahedral (Co2+, S = 3/2) structures exhibit distinct features, allowing unambiguous assignment of spin and oxidation states of the metal centers, as well as confirmation of the local geometry. Comparison with experimental spectra confirms that the high-spin tetrahedral geometry is realized in the supported framework, demonstrating how spectroscopic fingerprints can directly link coordination geometry to spin and oxidation states in low-dimensional metal-organic systems.

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Deliverables view all

WP2 - MGT2 - Pilot scheme for the management of a distributed research infrastructure offering harmonised, interoperable and integrated services

D2.8 - Second call for additional providers

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31 Jul 2025

Elisabetta Travaglia (CNR), Cristina Africh (CNR), Luis Fonseca (CSIC), Laura Esposito (CNR), Emmanuel Stratakis (FORTH), Giuseppe Piero Brandino (eXact lab), Giorgio Rossi (UniMI), Roberto Gotter (CNR)

According to the Grant Agreement, in the lifetime of NFFA-Europe Pilot the Transnational Access offer must enlarge to meet (i) the qualitative needs of users that could be better met with new specialized providers, or (ii) quantitative needs resulting in oversubscription of the current capacity. To this aim, two calls for additional access providers were foreseen at M24 and M40, respectively. This report describes the rationale that led to the text of the second call for additional access providers, i.e. from the evaluation of the needs – mainly based on the analysis provided in the deliverable D2.7 “Second balance of access provision” - to the search for alternative solutions to widen and strengthen the current offer.

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WP14 - JA4 - A safe-by-design platform for nanomaterials

D14.4 - Integration and characterization of the space correlation functionality on the complete setup

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31 May 2025

T. F. Keller (DESY), S. Kulkarni (DESY), H.A Suarez Orduz (ESRF), H. Castillo-Michel (ESRF)

This report presents an experimental workflow designed to perform correlative measurements as part of the NEP-NFFA project, using silicon nitride (Si3N4) membranes equipped with platinum (Pt) markers. These membranes were developed through a collaboration between DESY NanoLab and ESRF-ID21. DESY NanoLab was responsible for the Pt deposition on the Si3N4 membranes, while ESRF-ID21 carried out the correlative measurements. The purpose of the Pt markers on the membranes is to act as fiducial points that help to precisely locate specific regions or points of interest (ROI/POI) with micrometric or nanometric accuracy. This is essential to analyze the same point of the sample using different techniques, and to collect complementary data for a better understanding of the sample. The proposed workflow involves complementary techniques such as optical microscopy, scanning electron microscopy (SEM), and synchrotron-based techniques like micro X-ray fluorescence (µXRF) performed at the nano-X-ray microscope (nano-SXM) at beamline ID21 of the Softhis report describes the initial design of the membranes with the markers, as well as the optimized version, based on results obtained during the first tests with nano-SXM. In addition, it shows how the Pt markers enable accurate correlation through the web-based graphical interface Daiquiri, linking the morphological information from optical microscopy with the chemical information obtained from µXRF. The technical feasibility of this approach has been confirmed, showing that the process is reproducible and potentially applicable to similar studies. This is possible due to the standardized Pt deposition process and the use of nano-SXM for sample localization and data acquisition.

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WP14 - JA4 - A safe-by-design platform for nanomaterials

D14.5 - Production and report of three case studies with selected workflows

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31 May 2025

J. Linell (LUND), C. Isaxson (LUND), C. Abrahamsson (LUND), Maria Enea (INL) et al.

This report aims to demonstrate the usefulness of the NFFA workflow to assess nanomaterials and their interaction with different cell lines. It also seeks to generate improved protocols and educational material that can be shared with other European users working with similar ENMs.

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Transnational Access Statistics

31 calls for access

1176 proposals submitted

61% rate of acceptance

30% with Large Scale Facilities

13% with theory

12% with industry

~3 average users per proposal

66 countries applying

3653 lab sessions