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Condens. Matter, Volume 9, Issue 2 (June 2024) – 8 articles

Cover Story (view full-size image): The VIP-2 (VIolation of the Pauli exclusion principle-2) collaboration is conducting high-sensitivity experiments on foundational issues in quantum gravity and quantum mechanics within the low-background environment of the Gran Sasso underground laboratories of the INFN. Our recent phenomenological investigations predict a characteristic electromagnetic radiation signature for non-commutative quantum gravity and dynamical wave function collapse models in the keV range. This work details our ongoing efforts to optimize a prototype setup using a broad-energy germanium (BEGe) detector. The goal is to achieve a lower energy threshold in the order of keV and test the peculiar X-ray signature expected from selected targets with varying atomic structures. We discuss the current status of the activities, the challenges faced, and future plans. View this paper
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17 pages, 42688 KiB  
Article
The Multi-Detectors System of the PANDORA Facility: Focus on the Full-Field Pin-Hole CCD System for X-ray Imaging and Spectroscopy
by David Mascali, Eugenia Naselli, Sandor Biri, Giorgio Finocchiaro, Alessio Galatà, Giorgio Sebastiano Mauro, Maria Mazzaglia, Bharat Mishra, Santi Passarello, Angelo Pidatella, Richard Rácz, Domenico Santonocito and Giuseppe Torrisi
Condens. Matter 2024, 9(2), 28; https://doi.org/10.3390/condmat9020028 - 20 Jun 2024
Viewed by 847
Abstract
PANDORA (Plasmas for Astrophysics Nuclear Decays Observation and Radiation for Archaeometry) is an INFN project aiming at measuring, for the first time, possible variations in in-plasma β-decay lifetimes in isotopes of astrophysical interest as a function of thermodynamical conditions of the in-laboratory [...] Read more.
PANDORA (Plasmas for Astrophysics Nuclear Decays Observation and Radiation for Archaeometry) is an INFN project aiming at measuring, for the first time, possible variations in in-plasma β-decay lifetimes in isotopes of astrophysical interest as a function of thermodynamical conditions of the in-laboratory controlled plasma environment. Theoretical predictions indicate that the ionization state can dramatically modify the β-decay lifetime (even of several orders of magnitude). The PANDORA experimental approach consists of confining a plasma able to mimic specific stellar-like conditions and measuring the nuclear decay lifetime as a function of plasma parameters. The β-decay events will be measured by detecting the γ-ray emitted by the daughter nuclei, using an array of 12 HPGe detectors placed around the magnetic trap. In this frame, plasma parameters have to be continuously monitored online. For this purpose, an innovative, non-invasive multi-diagnostic system, including high-resolution time- and space-resolved X-ray analysis, was developed, which will work synergically with the γ-rays detection system. In this contribution, we will describe this multi-diagnostics system with a focus on spatially resolved high-resolution X-ray spectroscopy. The latter is performed by a pin-hole X-ray camera setup operating in the 0.5–20 keV energy domain. The achieved spatial and energy resolutions are 450 µm and 230 eV at 8.1 keV, respectively. An analysis algorithm was specifically developed to obtain SPhC (Single Photon-Counted) images and local plasma emission spectrum in High-Dynamic-Range (HDR) mode. Thus, investigations of image regions where the emissivity can change by even orders of magnitude are now possible. Post-processing analysis is also able to remove readout noise, which is often observable and dominant at very low exposure times (ms). Several measurements have already been used in compact magnetic plasma traps, e.g., the ATOMKI ECRIS in Debrecen and the Flexible Plasma Trap at LNS. The main outcomes will be shortly presented. The collected data allowed for a quantitative and absolute evaluation of local emissivity, the elemental analysis, and the local evaluation of plasma density and temperature. This paper also discusses the new plasma emission models, implemented on PIC-ParticleInCell codes, which were developed to obtain powerful 3D maps of the X-rays emitted by the magnetically confined plasma. These data also support the evaluation procedure of spatially resolved plasma parameters from the experimental spectra as well as, in the near future, the development of appropriate algorithms for the tomographic reconstruction of plasma parameters in the X-ray domain. The described setups also include the most recent upgrade, consisting of the use of fast X-ray shutters with special triggering systems that will be routinely implemented to perform both space- and time-resolved spectroscopy during transient, stable, and turbulent plasma regimes (in the ms timescale). Full article
(This article belongs to the Special Issue High Precision X-ray Measurements 2023)
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15 pages, 5612 KiB  
Article
Microstructure and Unusual Ferromagnetism of Epitaxial SnO2 Films Heavily Implanted with Co Ions
by Rustam I. Khaibullin, Amir I. Gumarov, Iskander R. Vakhitov, Andrey A. Sukhanov, Nikolay M. Lyadov, Airat G. Kiiamov, Dilyara M. Kuzina, Valery V. Bazarov and Almaz L. Zinnatullin
Condens. Matter 2024, 9(2), 27; https://doi.org/10.3390/condmat9020027 - 11 Jun 2024
Viewed by 1007
Abstract
In this work, we have studied the microstructure and unusual ferromagnetic behavior in epitaxial tin dioxide (SnO2) films implanted with 40 keV Co+ ions to a high fluence of 1.0 × 1017 ions/cm2 at room or elevated substrate [...] Read more.
In this work, we have studied the microstructure and unusual ferromagnetic behavior in epitaxial tin dioxide (SnO2) films implanted with 40 keV Co+ ions to a high fluence of 1.0 × 1017 ions/cm2 at room or elevated substrate temperatures. The aim was to comprehensively understand the interplay between cobalt implant distribution, crystal defects (such as oxygen vacancies), and magnetic properties of Co-implanted SnO2 films, which have potential applications in spintronics. We have utilized scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), differential thermomagnetic analysis (DTMA), and ferromagnetic resonance (FMR) to investigate Co-implanted epitaxial SnO2 films. The comprehensive experimental investigation shows that the Co ion implantation with high cobalt concentration induces significant changes in the microstructure of SnO2 films, leading to the appearance of ferromagnetism with the Curie temperature significantly above the room temperature. We also established a strong influence of implantation temperature and subsequent high-temperature annealing in air or under vacuum on the magnetic properties of Co-implanted SnO2 films. In addition, we report a strong chemical effect of ethanol on the FMR spectra. The obtained results are discussed within the model of two magnetic layers, with different concentrations and valence states of the implanted cobalt, and with a high content of oxygen vacancies. Full article
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12 pages, 1360 KiB  
Article
Enhancing Spectroscopic Experiment Calibration through Differentiable Programming
by Fabrizio Napolitano
Condens. Matter 2024, 9(2), 26; https://doi.org/10.3390/condmat9020026 - 5 Jun 2024
Viewed by 733
Abstract
In this work, we present an innovative calibration technique leveraging differentiable programming to enhance energy resolution and reduce the energy scale systematic uncertainty in X-ray spectroscopic experiments. This approach is demonstrated using synthetic data and is applicable in general to various spectroscopic measurements. [...] Read more.
In this work, we present an innovative calibration technique leveraging differentiable programming to enhance energy resolution and reduce the energy scale systematic uncertainty in X-ray spectroscopic experiments. This approach is demonstrated using synthetic data and is applicable in general to various spectroscopic measurements. This method extends the scope of differentiable programming for calibration, employing Kernel Density Estimation (KDE) to achieve a target Probability Density Function (PDF) for a fully differentiable model of the calibration. To assess the effectiveness of the calibration, we conduct a toy simulation replicating the entire detector response chain and compare it with a standard calibration. This ensures a robust and reliable calibration methodology, holding promise for improving energy resolution and providing a more versatile and efficient approach without the need for extensive fine-tuning. Full article
(This article belongs to the Special Issue High Precision X-ray Measurements 2023)
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16 pages, 329 KiB  
Article
The Effective Potential of Scalar Pseudo-Quantum Electrodynamics in (2 + 1)D
by Leandro O. Nascimento, Carlos A. P. C. Junior and José R. Santos
Condens. Matter 2024, 9(2), 25; https://doi.org/10.3390/condmat9020025 - 30 May 2024
Viewed by 917
Abstract
The description of the electron–electron interactions in two-dimensional materials has a dimensional mismatch, where electrons live in (2 + 1)D while photons propagate in (3 + 1)D. In order to define an action in (2 + 1)D, one may perform a dimensional reduction [...] Read more.
The description of the electron–electron interactions in two-dimensional materials has a dimensional mismatch, where electrons live in (2 + 1)D while photons propagate in (3 + 1)D. In order to define an action in (2 + 1)D, one may perform a dimensional reduction of quantum electrodynamics in (3 + 1)D (QED4) into pseudo-quantum electrodynamics (PQED). The main difference between this model and QED4 is the presence of a pseudo-differential operator in the Maxwell term. However, besides the Coulomb repulsion, electrons in a material are subjected to several microscopic interactions, which are inherent in a many-body system. These are expected to reduce the range of the Coulomb potential, leading to a short-range interaction. Here, we consider the coupling to a scalar field in PQED for explaining such a mechanism, which resembles the spontaneous symmetry breaking (SSB) in Abelian gauge theories. In order to do so, we consider two cases: (i) by coupling the quantum electrodynamics to a Higgs field in (3 + 1)D and, thereafter, performing the dimensional reduction; and (ii) by coupling a Higgs field to the gauge field in PQED and, subsequently, calculating its effective potential. In case (i), we obtain a model describing electrons interacting through the Yukawa potential and, in case (ii), we show that SSB does not occur at one-loop approximation. The relevance of the model for describing electronic interactions in two-dimensional materials is also addressed. Full article
(This article belongs to the Special Issue PQED: 30 Years of Reduced Quantum Electrodynamics)
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34 pages, 49917 KiB  
Editorial
Meeting and Working with K. Alex Müller: Personal Memories
by Annette Bussmann-Holder and Hugo Keller
Condens. Matter 2024, 9(2), 24; https://doi.org/10.3390/condmat9020024 - 8 May 2024
Viewed by 1037
Abstract
On 9 January 2023, K [...] Full article
(This article belongs to the Special Issue Complexity in Quantum Materials: In Honor of Prof. K.A. Muller)
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7 pages, 2671 KiB  
Editorial
Alex’s Vision in Functional Quantum Matter
by Davor Pavuna
Condens. Matter 2024, 9(2), 23; https://doi.org/10.3390/condmat9020023 - 18 Apr 2024
Viewed by 899
Abstract
My ‘In Memoriam’ contribution is very personal, as it includes many human and professional insights that I received from Alex Müller himself [...] Full article
(This article belongs to the Special Issue Complexity in Quantum Materials: In Honor of Prof. K.A. Muller)
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12 pages, 4765 KiB  
Article
Optimization of a BEGe Detector Setup for Testing Quantum Foundations in the Underground LNGS Laboratory
by Kristian Piscicchia, Alberto Clozza, Diana Laura Sirghi, Massimiliano Bazzi, Nicola Bortolotti, Mario Bragadireanu, Michael Cargnelli, Luca De Paolis, Raffaele Del Grande, Carlo Guaraldo, Mihail Iliescu, Matthias Laubenstein, Simone Manti, Johann Marton, Marco Miliucci, Fabrizio Napolitano, Alessio Porcelli, Alessandro Scordo, Francesco Sgaramella, Florin Sirghi, Sandro Tomassini, Oton Vazquez Doce, Johann Zmeskal and Catalina Curceanuadd Show full author list remove Hide full author list
Condens. Matter 2024, 9(2), 22; https://doi.org/10.3390/condmat9020022 - 11 Apr 2024
Viewed by 1089
Abstract
In this work, we report on tests performed with an experimental apparatus prototype based on a broad-energy germanium detector aimed at investigating topical, foundational issues in quantum mechanics: i.e., possible violations of the spin-statistics connection and models of dynamical wave function collapse. Our [...] Read more.
In this work, we report on tests performed with an experimental apparatus prototype based on a broad-energy germanium detector aimed at investigating topical, foundational issues in quantum mechanics: i.e., possible violations of the spin-statistics connection and models of dynamical wave function collapse. Our recent phenomenological analyses demonstrated the importance of pushing the research of new physics signal, predicted in these fields, to an energy range below 10 keV. We describe the development of the dedicated data acquisition system and of the pulse shape discrimination algorithm, which have already allowed us to get a factor two improvement in the lower energy threshold. Future plans are discussed to further improve the lower energy threshold to the level of a few keV. Full article
(This article belongs to the Special Issue High Precision X-ray Measurements 2023)
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9 pages, 449 KiB  
Review
Superconductors without Symmetry Breaking
by Maria Cristina Diamantini
Condens. Matter 2024, 9(2), 21; https://doi.org/10.3390/condmat9020021 - 2 Apr 2024
Viewed by 1388
Abstract
We review the main features of type-III superconductivity. This is a new type of superconductivity that exists in both 2 and 3 spatial dimensions. The main characteristics are emergent granularity and the superconducting gap being opened by a topological mechanism, with no Higgs [...] Read more.
We review the main features of type-III superconductivity. This is a new type of superconductivity that exists in both 2 and 3 spatial dimensions. The main characteristics are emergent granularity and the superconducting gap being opened by a topological mechanism, with no Higgs field involved. Superconductivity is destroyed by the proliferation of vortices and not by the breaking of Cooper pairs, which survive above the critical temperature. The hallmark of this superconductivity mechanism, in 3 spatial dimensions (3D), is the Vogel–Fulcher–Taman scaling of the resistance with temperature. Full article
(This article belongs to the Special Issue Superstripes Physics, 2nd Edition)
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