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Condensed Matter

Condensed Matter is an international, peer-reviewed, open access journal on the physics of condensed matter published quarterly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, ESCI (Web of Science), Inspec, CAPlus / SciFinder, and other databases.
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 20.1 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the first half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 1.5 (2024); 5-Year Impact Factor: 1.5 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2410-3896

Latest Articles

12 pages, 674 KB

Open AccessArticle

Role of the Electron–Phonon Interaction in the Superconductivity of the 2-Dimensional Sn/Si(111) Interface

by Fernando Flores, Daniel G. Trabada, Álvaro Martín-Rodero and José Ortega

Condens. Matter 2025, 10(3), 51; https://doi.org/10.3390/condmat10030051 - 15 Sep 2025

In order to elucidate the mechanism creating superconductivity in the 2-dimensional layer of a p-doped Sn/Si(111) surface, we have analyzed the many-body effects associated with the electron-phonon (e-ph) coupling and the electron–electron interaction. First, we have calculated the DFT surface band of the [...] Read more.

In order to elucidate the mechanism creating superconductivity in the 2-dimensional layer of a p-doped Sn/Si(111) surface, we have analyzed the many-body effects associated with the electron-phonon (e-ph) coupling and the electron–electron interaction. First, we have calculated the DFT surface band of the system and the coupling associated with the different interactions. In our calculations we find a mean field (DFT) electron bandwidth of 0.54 eV, an attractive coupling

U^{n e g} = 0.32

eV associated with the e-ph coupling and an effective electron–electron Hubbard repulsion of

U = 0.83

eV. Then, we analyze the Hubbard Hamiltonian, neglecting in this step the e-ph coupling that is much smaller than the Hubbard coupling, by considering a p-doping in this Hamiltonian of 10%; by means of a Dynamical Mean Field (DMF) approach combined with an interpolative calculation for the self-energy, we deduce the local density of states (DOS) and show that the quasi-particle DOS induced by the doping is not large enough to induce magnetism in the Sn-monolayer. This leads us to analyze the possibility of having superconductivity by considering the attractive interaction induced by the e-ph coupling within an appropriate BCS-Hamiltonian. Our calculations show that the quasiparticle metallic system has a superconductivity critical temperature of ≈7–9 K, in good agreement with experiments. Full article

(This article belongs to the Special Issue New Advances in Condensed Matter Physics, 2nd Edition)

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30 pages, 52059 KB

Open AccessArticle

Geometry-Driven Tunability of Edge States in Topological Core–Shell Nanowires

by Nicolás Legnazzi and Omar Osenda

Condens. Matter 2025, 10(3), 50; https://doi.org/10.3390/condmat10030050 - 13 Sep 2025

The study of new nanoscopic heterostructures composed of different materials follows the idea that the presence of boundary conditions, interfaces and combinations of materials will produce appropriate spectral properties or quantum states, resulting in new devices. Here, we present a detailed study of [...] Read more.

The study of new nanoscopic heterostructures composed of different materials follows the idea that the presence of boundary conditions, interfaces and combinations of materials will produce appropriate spectral properties or quantum states, resulting in new devices. Here, we present a detailed study of two kinds of nanowires formed using topological insulators. First, we consider cylindrical nanowires with a cylindrical core of constant radius along the wire, covered by a shell of uniform width. The core and the shell materials are different topological insulators. We thoroughly study the spectra of distinct wires, considering combinations of materials and sizes of the core and shell radii. We also study the expectation values of the spin operators. Then, we consider wires with only a cylindrical shell. For this case, we pay special attention to the limit when the width of the shell is approximately an order of magnitude smaller than the inner and outer radii of the shell. As we use a high-accuracy variational method to obtain the spectra and quantum states, we also study information-like quantities such as the fidelity and quantum entropy of the topological and normal states of the wires. Full article

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12 pages, 1987 KB

Open AccessArticle

The Superconducting Properties of Elemental Pb Under Pressure

by Shu-Ke Xuan, Yuan-Fang Yue, Xiao-Ming Li and Xun-Wang Yan

Condens. Matter 2025, 10(3), 49; https://doi.org/10.3390/condmat10030049 - 12 Sep 2025

Based on first-principles calculations, we systematically investigate the crystal structure, electronic structure, and superconductivity of metallic lead under pressure. The results show that with the increase of pressure, the crystal structure of lead evolves from face-centered cubic (fcc) to hexagonal close-packed (hcp) and [...] Read more.

Based on first-principles calculations, we systematically investigate the crystal structure, electronic structure, and superconductivity of metallic lead under pressure. The results show that with the increase of pressure, the crystal structure of lead evolves from face-centered cubic (fcc) to hexagonal close-packed (hcp) and then to body-centered cubic (bcc). In different crystal structure phases, the variation laws of electronic structure and superconducting properties with pressure are studied. It is found that the superconducting transition temperature decreases with the increase of pressure in fcc, hcp, and bcc phases. The physical mechanism for this change is explained. The calculation results indicate that elemental metallic lead remains metallic with the increase of pressure, but the electron density of states at the Fermi level decreases, leading to the decrease of the electron-phonon coupling constant (

λ

) and superconducting transition temperature (

T_{c}

) from 7.1 K to 0.04 K. In addition, with the increase of pressure, there is no phenomenon of s electrons transforming into d electrons, which is different from the superconducting behavior of zirconium metal under pressure. These studies explain the superconductivity of elemental metallic lead under high pressure and provide theoretical support for the experiments and applications of lead-based superconductors. Full article

(This article belongs to the Section Superconductivity)

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20 pages, 3263 KB

Open AccessArticle

The Response of a Linear, Homogeneous and Isotropic Dielectric and Magnetic Sphere Subjected to an External Field, DC or Low-Frequency AC, of Any Form

by Dimosthenis Stamopoulos

Condens. Matter 2025, 10(3), 48; https://doi.org/10.3390/condmat10030048 - 1 Sep 2025

Cited by 1

Maxwell’s equations epitomize our knowledge of standard electromagnetic theory in vacuums and matter. Here, we report the clearcut results of an extensive, ongoing investigation aiming to mathematically digest Maxwell’s equations in virtually all problems based on the three standard building units, dielectric and [...] Read more.

Maxwell’s equations epitomize our knowledge of standard electromagnetic theory in vacuums and matter. Here, we report the clearcut results of an extensive, ongoing investigation aiming to mathematically digest Maxwell’s equations in virtually all problems based on the three standard building units, dielectric and magnetic, found in practice (i.e., spheres, cylinders and plates). Specifically, we address the static/quasi-static case of a linear, homogeneous and isotropic dielectric and magnetic sphere subjected to a DC/low-frequency AC external scalar potential, (vector field, ), of any form, produced by a primary/free source residing outside the sphere. To this end, we introduce an expansion-based mathematical strategy that enables us to obtain immediate access to the response of the dielectric and magnetic sphere, i.e., to the internal scalar potential, (vector field, ), produced by the induced secondary/bound source. Accordingly, the total scalar potential, = + (vector field, = + ), is immediately accessible as well. Our approach provides ready-to-use expressions for and ( and ) in all space, i.e., both inside and outside the dielectric and magnetic sphere, applicable for any form of (). Using these universal expressions, we can obtain and ( and ) in essentially one step, without the need to solve each particular problem of different () every time from scratch. The obtained universal relation between and ( and ) provides a means to tailor the responses of dielectric and magnetic spheres at all instances, thus facilitating applications. Our approach surpasses conventional mathematical procedures that are employed to solve analytically addressable problems of electromagnetism. Full article

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8 pages, 253 KB

Open AccessPerspective

Very High-Energy Cosmic Ray Particles from the Kerr Black Hole at the Galaxy Center

by Orlando Panella, Simone Pacetti, Giorgio Immirzi and Yogendra Srivastava

Condens. Matter 2025, 10(3), 47; https://doi.org/10.3390/condmat10030047 - 23 Aug 2025

After a just tribute to Guido Barbiellini, we show how the notion of a maximum force (

F_{\max} = c^{4} / (4 G) ≃ 3 \times 10^{43}

Newtons) present on the event horizon of a black hole (BH) can be [...] Read more.

After a just tribute to Guido Barbiellini, we show how the notion of a maximum force (

F_{\max} = c^{4} / (4 G) ≃ 3 \times 10^{43}

Newtons) present on the event horizon of a black hole (BH) can be used in conjunction with the Wilson area rule to obtain the surface confinement of the mass of a BH analogous to the surface confinement of quarks. This is then translated into the central result of the paper that PeV scale protons exist on the surface of the Kerr BH residing at our galactic center, a result in complete agreement with the HAWC Collaboration result of a Pevatron at the galactic center. We conjecture that the supermassive BHs present at the center of most galaxies are not born out of a galactic collapse but that they must have been present since the formation of their hosting galaxy. Full article

(This article belongs to the Special Issue The Universe Observed With Particle Detectors: Celebrating the Scientific Legacy of Prof. Guido Barbiellini Amidei)

10 pages, 701 KB

Open AccessArticle

Beyond Wave-Nature Signatures: h-Independent Transport in Strongly-Scattering Quasi-2D Quantum Channels

by Er’el Granot

Condens. Matter 2025, 10(3), 46; https://doi.org/10.3390/condmat10030046 - 14 Aug 2025

The Landauer-Büttiker formalism provides a fundamental framework for mesoscopic transport, typically expressing conductance in units of the quantum of conductance, e²/h. Here, we present a theoretical study of electron transport in a quasi two-dimensional (2D) quantum wire. This system [...] Read more.

The Landauer-Büttiker formalism provides a fundamental framework for mesoscopic transport, typically expressing conductance in units of the quantum of conductance, e²/h. Here, we present a theoretical study of electron transport in a quasi two-dimensional (2D) quantum wire. This system features a wide transverse confinement and a longitudinal, high-energy, narrow potential barrier. The derivation, performed within the Landauer framework, yields an analytical expression for the total conductance that is explicitly independent of Planck’s constant (h). Instead, the conductance is found to depend solely on the Fermi energy, the electron effective mass, the wire width, and the effective barrier strength. We interpret this as an emergent phenomenon where the explicit signature of the electron’s wave-like nature, commonly manifest through Planck’s constant (h) in the overall scaling of conductance, is effectively absorbed within the energy- and geometry-dependent sum of transmission probabilities. This allows the conductance to be primarily governed by the Fermi energy, representing a ‘state-counting’ quantum parameter rather than more wave-like characteristic. Full article

(This article belongs to the Section Quantum Materials)

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13 pages, 346 KB

Open AccessArticle

The Solution to Hardy’s Paradox

by Ivan Arraut

Condens. Matter 2025, 10(3), 45; https://doi.org/10.3390/condmat10030045 - 10 Aug 2025

By using both the weak-value formulation as well as the standard probabilistic approach, we analyze Hardy’s experiment introducing a complex and dimensionless parameter (

ϵ

), which eliminates the assumption of complete annihilation when both the electron and the positron departing from a [...] Read more.

By using both the weak-value formulation as well as the standard probabilistic approach, we analyze Hardy’s experiment introducing a complex and dimensionless parameter (

ϵ

), which eliminates the assumption of complete annihilation when both the electron and the positron departing from a common origin cross the intersection point P. We then find that the paradox does not exist for all the possible values taken by the parameter. The apparent paradox only appears when

ϵ = 1

, which is just a singular value. In this paper we demonstrate that this particular value is forbidden inside the scenario proposed by the experiment. Full article

(This article belongs to the Section Condensed Matter Theory)

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15 pages, 5436 KB

Open AccessArticle

Effect of Surface Passivation on the Quasi-Two-Dimensional Perovskite X₂Cs_(n−1) Pb_nI_(3n+1)

by Min Li, Haoyan Zheng, Xianliang Ke, Dawei Zhang and Jie Huang

Condens. Matter 2025, 10(3), 44; https://doi.org/10.3390/condmat10030044 - 9 Aug 2025

The two-dimensional (2D) Ruddlesden–Popper perovskite exhibits superior chemical stability but suffers from compromised photoelectric properties due to the van der Waals gap. This study presents a novel investigation of surface passivation effects on quasi-2D perovskite X₂Cs_n−1Pb_nI_3n+1 [...] Read more.

The two-dimensional (2D) Ruddlesden–Popper perovskite exhibits superior chemical stability but suffers from compromised photoelectric properties due to the van der Waals gap. This study presents a novel investigation of surface passivation effects on quasi-2D perovskite X₂Cs_n−1Pb_nI_3n+1 (n = 1–6; X = MA, FA, PEA) using DFT methods, revealing three key advances: First, we demonstrate that organic cation passivation (MA⁺, FA⁺, PEA⁺) enables exceptional stability improvements, with FA-passivated structures showing optimal stability—a crucial finding for materials design. Second, we identify a critical thickness effect (n > 3) where bandgaps converge to <1.6 eV (approaching bulk values) while maintaining strong absorption, establishing the minimum layer requirement for optimal performance. Third, we reveal that effective masses balance and absorption strengthens significantly when n > 3. These fundamental insights provide a transformative strategy to simultaneously enhance both stability and optoelectronic properties in quasi-2D perovskites. Full article

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11 pages, 223 KB

Open AccessEssay

Beyond Space and Time: Quantum Superposition as a Real-Mental State About Choices

by Antoine Suarez

Condens. Matter 2025, 10(3), 43; https://doi.org/10.3390/condmat10030043 - 6 Aug 2025

This contribution aims to honour Guido Barbiellini’s profound interest in the interpretation and impact of quantum mechanics by examining the implications of the so-called before–before Experiment on quantum entanglement. This experiment was inspired by talks and discussions with John Bell at CERN. This [...] Read more.

This contribution aims to honour Guido Barbiellini’s profound interest in the interpretation and impact of quantum mechanics by examining the implications of the so-called before–before Experiment on quantum entanglement. This experiment was inspired by talks and discussions with John Bell at CERN. This was during the years when John and Guido co-worked, promoting the mission of the laboratory: “to advance the boundaries of human knowledge”. As the experiment uses measuring devices in motion, it can be considered a complement to entanglement experiments using stationary measuring devices, which have meanwhile been awarded the 2022 Nobel Prize in Physics. The before–before Experiment supports the idea that the quantum realm exists beyond space and time and that the quantum state is a real mental entity concerning choices. As it also leads us to a better understanding of the ‘quantum collapse’ and the measurement process, we pay homage to Guido’s work on detectors, such as his collaborations on the DELPHI experiment at CERN, on cosmic ray detection at the International Space Station, and gamma-ray astrophysics during a large NASA space mission. Full article

(This article belongs to the Special Issue The Universe Observed With Particle Detectors: Celebrating the Scientific Legacy of Prof. Guido Barbiellini Amidei)

8 pages, 2120 KB

Open AccessPerspective

Axion Searches at the CERN SPS: From Their Dawn to Current Prospects

by Paolo Crivelli and Martina Mongillo

Condens. Matter 2025, 10(3), 42; https://doi.org/10.3390/condmat10030042 - 5 Aug 2025

This mini-review traces the evolution of axion searches at the CERN Super Proton Synchrotron (SPS), beginning with the early proposal by Guido Barbiellini in 1982 and culminating in the recent advances of the NA62 and NA64 experiments. We discuss the experimental strategies employed [...] Read more.

This mini-review traces the evolution of axion searches at the CERN Super Proton Synchrotron (SPS), beginning with the early proposal by Guido Barbiellini in 1982 and culminating in the recent advances of the NA62 and NA64 experiments. We discuss the experimental strategies employed in early beam dump searches, the current status of axion and axion-like particle (ALP) searches at the CERN SPS and future directions. This review serves as a tribute to Guido Barbiellini’s scientific legacy and his visionary contributions to this field. Full article

(This article belongs to the Special Issue The Universe Observed With Particle Detectors: Celebrating the Scientific Legacy of Prof. Guido Barbiellini Amidei)

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11 pages, 1745 KB

Open AccessArticle

Comprehensive Investigation of Structural and Photocatalytic Properties of Cobalt and Nickel Co-Doped Magnesium Oxide Nanoparticles

by Shafaq Arif, Amna Sarwar and M. S. Anwar

Condens. Matter 2025, 10(3), 41; https://doi.org/10.3390/condmat10030041 - 4 Aug 2025

Cobalt and Nickel (Co, Ni) co-doped magnesium oxide (MgO) nanoparticles (NPs) have been synthesized using the coprecipitation method. The structural, chemical, and optical properties of the as-synthesized NPs are systematically investigated using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and UV-visible spectroscopy. [...] Read more.

Cobalt and Nickel (Co, Ni) co-doped magnesium oxide (MgO) nanoparticles (NPs) have been synthesized using the coprecipitation method. The structural, chemical, and optical properties of the as-synthesized NPs are systematically investigated using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and UV-visible spectroscopy. It is found that the optical bandgap of co-doped MgO NPs reduces from 2.30 to 1.98 eV (14%) with increasing Ni dopant concentrations up to 7%. The Co_0.05Ni_0.07Mg_0.88O NPs exhibit a high photocatalytic degradation efficiency of 93% for methylene blue dye (MB) under natural sunlight irradiation for 240 min. Our findings indicate that the Co_0.05Ni_xMg_0.95−xO NPs have strong potential for use as photocatalysts in industrial wastewater treatment. Full article

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11 pages, 962 KB

Open AccessArticle

Possible Realization of Hyperbolic Plasmons in Few-Layered Rhenium Disulfide

by Ravi Kiran, Dimitar Pashov, Mark van Schilfgaarde, Mikhail I. Katsnelson, Arghya Taraphder and Swagata Acharya

Condens. Matter 2025, 10(3), 40; https://doi.org/10.3390/condmat10030040 - 19 Jul 2025

Hyperbolic plasmons are a highly desired property in optoelectronics and biomolecular sensing. The necessary condition to realize hyperbolic plasmons is a significant anisotropy of the principal components of the dielectric function, such that at a certain frequency range, one component is negative and [...] Read more.

Hyperbolic plasmons are a highly desired property in optoelectronics and biomolecular sensing. The necessary condition to realize hyperbolic plasmons is a significant anisotropy of the principal components of the dielectric function, such that at a certain frequency range, one component is negative and the other is positive, i.e., one component is metallic, and the other one is dielectric. Here, we study the effect of anisotropy in

{ReS}_{2}

, and our theory shows that

{ReS}_{2}

can host hyperbolic plasmons in the ultraviolet frequency range. The operating frequency range of the hyperbolic plasmons can be tuned with the number of

{ReS}_{2}

layers. However, we note that the significantly large imaginary part of the macroscopic dielectric response in all layered variants of ReS₂ can result in substantial losses for the hyperbolic plasmons, as in the case with other known hyperbolic materials, with the exception of MoOCl₂. We also note that ReS₂ hosts ultraviolet hyperbolic plasmons while ZrSiSe, WTe₂, and CuS nanocrystals host infrared plasmons, providing a novel platform for optoelectronics in the ultraviolet range. Full article

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16 pages, 1799 KB

Open AccessArticle

Skyrmion Crystal in Bilinear–Biquadratic–Bicubic Model on a Centrosymmetric Triangular Lattice

by Satoru Hayami

Condens. Matter 2025, 10(3), 39; https://doi.org/10.3390/condmat10030039 - 18 Jul 2025

We numerically investigate the effect of multi-spin interactions on the stability of skyrmion crystals and other multiple-Q magnetic states, with a particular emphasis on the momentum-resolved bicubic interaction. By performing simulated annealing for an effective spin model that incorporates bilinear, biquadratic, and [...] Read more.

We numerically investigate the effect of multi-spin interactions on the stability of skyrmion crystals and other multiple-Q magnetic states, with a particular emphasis on the momentum-resolved bicubic interaction. By performing simulated annealing for an effective spin model that incorporates bilinear, biquadratic, and bicubic interactions on a two-dimensional triangular lattice, we construct the corresponding low-temperature phase diagram. Our results reveal that a positive bicubic interaction stabilizes a skyrmion crystal with a skyrmion number of two, whereas a negative bicubic interaction favors a single-Q spiral state. Moreover, we demonstrate that the stability region of the field-induced skyrmion crystal with the skyrmion number of one is largely enlarged in the presence of a positive bicubic interaction. Full article

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24 pages, 7332 KB

Open AccessArticle

High-Performance Natural Dye-Sensitized Solar Cells Employing a New Semiconductor: Gd₂Ru₂O₇ Pyrochlore Oxide

by Assohoun F. Kraidy, Abé S. Yapi, Joseph K. Datte, Michel Voue, Mimoun El Marssi, Anthony Ferri and Yaovi Gagou

Condens. Matter 2025, 10(3), 38; https://doi.org/10.3390/condmat10030038 - 14 Jul 2025

We investigated a novel natural dye-sensitized solar cell (DSSC) utilizing gadolinium ruthenate pyrochlore oxide Gd₂Ru₂O₇ (GRO) as a photoanode and compared its performance to the TiO₂-Gd₂Ru₂O₇ (TGRO) combined-layer configuration. The films [...] Read more.

We investigated a novel natural dye-sensitized solar cell (DSSC) utilizing gadolinium ruthenate pyrochlore oxide Gd₂Ru₂O₇ (GRO) as a photoanode and compared its performance to the TiO₂-Gd₂Ru₂O₇ (TGRO) combined-layer configuration. The films were fabricated using the spin-coating technique, resulting in spherical grains with an estimated mean diameter of 0.2 µm, as observed via scanning electron microscopy (SEM). This innovative photoactive gadolinium ruthenate pyrochlore oxide demonstrated strong absorption in the visible range and excellent dye adhesion after just one hour of exposure to natural dye. X-ray diffraction confirmed the presence of the pyrochlore phase, where Raman spectroscopy identified various vibration modes characteristic of the pyrochlore structure. Incorporating Gd₂Ru₂O₇ as the photoanode significantly enhanced the overall efficiency of the DSSCs. The device configuration FTO/compact-layer/Gd₂Ru₂O₇/Hibiscus-sabdariffa/electrolyte(I⁻/I₃⁻)/Pt achieved a high efficiency of 9.65%, an open-circuit voltage (Voc) of approximately 3.82 V, and a current density of 4.35 mA/cm² for an active surface area of 0.38 cm². A mesoporous TiO₂-based DSSC was fabricated under the same conditions for comparison. Using impedance spectroscopy and cyclic voltammetry measurements, we provided evidence of the mechanism of conductivity and the charge carrier’s contribution or defect contributions in the DSSC cells to explain the obtained Voc value. Through cyclic voltammetry measurements, we highlight the redox activities of hibiscus dye and electrolyte (I⁻/I₃⁻), which confirmed electrochemical processes in addition to a photovoltaic response. The high and unusual obtained Voc value was also attributed to the presence in the photoanode of active dipoles, the layer thickness, dye concentration, and the nature of the electrolyte. Full article

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5 pages, 197 KB

Open AccessCommunication

Nevanlinna Analytical Continuation of the Central Charge in 2D Conformal Field Theory

by Bernardo Barbiellini

Condens. Matter 2025, 10(3), 37; https://doi.org/10.3390/condmat10030037 - 8 Jul 2025

We present an analytic continuation of the central charge c in two-dimensional conformal field theory (2D CFT), modeled as a Nevanlinna function—an analytic map from the upper half-plane to itself. Motivated by the structure of vacuum energies arising from the quantization of spin- [...] Read more.

We present an analytic continuation of the central charge c in two-dimensional conformal field theory (2D CFT), modeled as a Nevanlinna function—an analytic map from the upper half-plane to itself. Motivated by the structure of vacuum energies arising from the quantization of spin-j conformal fields on the circle, we derive a discrete spectrum of central charges

c (j) = 1 + 6 j (j + 1)

and extend it continuously via

c (z) = 1 + 6 z

. The Möbius-inverted form

f (z) = 1 - 6 / z

satisfies the conditions of a Nevanlinna function, providing a physically consistent analytic structure that captures both the unitarity of minimal models (

c < 1

) and the continuous spectrum for

c \geq 1

. This unified framework highlights the connection between spectral theory, analyticity, and conformal symmetry in quantum field theory. Full article

(This article belongs to the Special Issue The Universe Observed With Particle Detectors: Celebrating the Scientific Legacy of Prof. Guido Barbiellini Amidei)

18 pages, 1546 KB

Open AccessArticle

Ultrasound-Assisted Synthesis for the Control of Silver Nanoparticle Size: A Preliminary Study on the Influence of Pressure and pH

by Paula Riascos, Daniel Llamosa, Jahaziel Amaya and Hansen Murcia

Condens. Matter 2025, 10(3), 36; https://doi.org/10.3390/condmat10030036 - 7 Jul 2025

The use of plasmonic nanoparticles for biosensor technology is dependent on nanoparticle size and morphology. This study determined the effect of pH and pressure on synthesizing silver nanoparticle size. In Method 1, a mixture of NaBH₄ and sodium citrate was added to [...] Read more.

The use of plasmonic nanoparticles for biosensor technology is dependent on nanoparticle size and morphology. This study determined the effect of pH and pressure on synthesizing silver nanoparticle size. In Method 1, a mixture of NaBH₄ and sodium citrate was added to a solution of AgNO₃ monodispersed by ultrasound energy. In Method 2, the reducer was added to the precursor–dispersant mixture solution. The effect of pH was evaluated by using buffer solutions at pH 4.0, pH 7.0, and pH 10.0 and water as control. To determine the effect of pressure, AgNPs were subjected to 0, 4, and 23 h to 1.75 MPa at 200 °C. AgNPs produced with Method 1 showed a more symmetric SPR and a smaller nanoparticle diameter (±6 nm). The SPR with Method 1 at pH 10.0 produced a higher UV peak with a shift around 20 nm. In the case of the pressure treatment, a shift of approximately 20 nm was observed at all time conditions studied, and a higher AgNP diameter was found in contrast to Method 1. Finally, EDX and Raman analysis confirm the presence of AgNPs and a mild oxidation of these. These results suggest that alkalinity and pressure can affect the diameter of AgNPs. Full article

(This article belongs to the Section Physics of Materials)

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15 pages, 803 KB

Open AccessArticle

Field-Induced Ferroaxiality in Antiferromagnets with Magnetic Toroidal Quadrupole

by Satoru Hayami

Condens. Matter 2025, 10(2), 35; https://doi.org/10.3390/condmat10020035 - 14 Jun 2025

Magnetic toroidal multipoles have recently emerged as key descriptors of unconventional cross-correlation phenomena in antiferromagnetic systems. Among them, the rank-2 magnetic toroidal quadrupole, which is characterized as a time-reversal-odd polar tensor, has been theoretically associated with a variety of cross-correlation phenomena arising from [...] Read more.

Magnetic toroidal multipoles have recently emerged as key descriptors of unconventional cross-correlation phenomena in antiferromagnetic systems. Among them, the rank-2 magnetic toroidal quadrupole, which is characterized as a time-reversal-odd polar tensor, has been theoretically associated with a variety of cross-correlation phenomena arising from the time-reversal symmetry breaking. In this study, we investigate the interplay between magnetic toroidal quadrupoles and electric toroidal dipoles in antiferromagnets, with a particular focus on magnetic field-induced ferroaxiality. Through symmetry analysis and microscopic model calculations, we demonstrate that ferroaxiality can be induced by an external magnetic field, depending on both the field direction and the type of the magnetic toroidal quadrupole. We classify all magnetic point groups that possess magnetic toroidal quadrupoles and identify various candidate materials based on the MAGNDATA database. Our findings reveal a route to coupling spin and lattice degrees of freedom via toroidal multipoles. Full article

(This article belongs to the Section Magnetism)

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8 pages, 227 KB

Open AccessPerspective

The Standard Model of Particle Physics and What Lies Beyond: A View from the Bridge

by Pran Nath

Condens. Matter 2025, 10(2), 34; https://doi.org/10.3390/condmat10020034 - 13 Jun 2025

The standard models of particle physics and of cosmology have been enormously successful in correlating a large amount of data. However, there are missing pieces and we are still far from what the ultimate model may look like. We give a broad perspective [...] Read more.

The standard models of particle physics and of cosmology have been enormously successful in correlating a large amount of data. However, there are missing pieces and we are still far from what the ultimate model may look like. We give a broad perspective of both the achievements and of the missing pieces and discuss what may lie beyond. Full article

(This article belongs to the Special Issue The Universe Observed With Particle Detectors: Celebrating the Scientific Legacy of Prof. Guido Barbiellini Amidei)

8 pages, 2029 KB

Open AccessArticle

Mott Law exp(T₀/T)^1/4 and Scaling Properties of the Oxygen-Deficient Tenorite CuO_0.75

by Danijel Djurek, Mladen Prester, Djuro Drobac, Vilko Mandić and Damir Pajić

Condens. Matter 2025, 10(2), 33; https://doi.org/10.3390/condmat10020033 - 11 Jun 2025

The novel sub-stoichiometric copper oxide CuO_0.75 was prepared via the slow oxidation of Cu₂O. This compound retains the original crystallographic structure of tenorite CuO, despite the considerable presence of disordered oxygen vacancies. CuO_0.75 resembles the mixed valence oxide Cu [...] Read more.

The novel sub-stoichiometric copper oxide CuO_0.75 was prepared via the slow oxidation of Cu₂O. This compound retains the original crystallographic structure of tenorite CuO, despite the considerable presence of disordered oxygen vacancies. CuO_0.75 resembles the mixed valence oxide Cu²⁺/Cu¹⁺, while the unit cell contains one oxygen vacancy. Performance-wise, the electric resistivity and magnetic susceptibility data follow the Anderson–Mott localization theories. The exponential localization decay length was found to be α⁻¹ = 2.1 nm, in line with modern scaling research. Via cooling, magnetic double-exchange interaction, mediated by oxygen, results in Zener conductivity at T~122 K, which is followed by antiferromagnetic transition at T~51 K. The obtained results indicate that the CuO_0.75 compound can be perceived as a showcase material for the demonstration of a new class of high-performance magnetic materials. Full article

(This article belongs to the Section Physics of Materials)

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11 pages, 232 KB

Open AccessReview

Antimatter Research at the CERN Antiproton Decelerator: Legacy of Guido Barbiellini Amidei

by Rafael Ferragut

Condens. Matter 2025, 10(2), 32; https://doi.org/10.3390/condmat10020032 - 3 Jun 2025

This work reviews the current research directions pursued by collaborations at CERN’s Antiproton Decelerator (AD), with an outlook on future perspectives and challenges in the field. The advancement of precision studies on antimatter builds upon foundational contributions by pioneering researchers, such as Guido [...] Read more.

This work reviews the current research directions pursued by collaborations at CERN’s Antiproton Decelerator (AD), with an outlook on future perspectives and challenges in the field. The advancement of precision studies on antimatter builds upon foundational contributions by pioneering researchers, such as Guido Barbiellini Amidei, whose early work on antimatter detection and instrumentation has profoundly influenced the design and methodologies of contemporary experiments at the AD and beyond. This review underscores the lasting impact of these early innovations on ongoing investigations into fundamental symmetries and interactions involving antimatter. Full article

(This article belongs to the Special Issue The Universe Observed With Particle Detectors: Celebrating the Scientific Legacy of Prof. Guido Barbiellini Amidei)

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