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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 20.8 days after submission; acceptance to publication is undertaken in 3.4 days (median values for papers published in this journal in the second 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 (2025); 5-Year Impact Factor: 1.6 (2025)

Imprint Information Journal Flyer Open Access ISSN: 2410-3896

Latest Articles

28 pages, 2121 KB

Open AccessArticle

Using Machine-Learned Force Fields for Describing Heat-Transport-Related Quantities in AlGaN and Derived Materials

by Simon Fernbach, Egbert Zojer and Natalia Bedoya-Martínez

Condens. Matter 2026, 11(2), 23; https://doi.org/10.3390/condmat11020023 - 11 Jun 2026

In this work, we develop machine-learned moment tensor potentials (MTPs) to simulate the static and dynamic structural properties in Al_xGa_1−xN and related materials. The potentials are trained on DFT-calculated data for forces, stresses, and energies obtained from random [...] Read more.

In this work, we develop machine-learned moment tensor potentials (MTPs) to simulate the static and dynamic structural properties in Al_xGa_1−xN and related materials. The potentials are trained on DFT-calculated data for forces, stresses, and energies obtained from random atomic displacements and cell deformations. MTP-calculated physical properties, including lattice parameters and elastic constants, thermal expansion, harmonic and anharmonic vibrational properties, and the thermal conductivity, are benchmarked against first-principles results and experimental data. The comparisons testify to the very high accuracy achieved by the machine-learned potentials despite the massively reduced computational effort. Additionally, the impact of various aspects of the MTP training procedure is examined. Full article

(This article belongs to the Special Issue 10th Anniversary of Condensed Matter: Recent Advances in Condensed Matter Physics)

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8 pages, 195 KB

Open AccessOpinion

The Universe Observed with Particle Detectors: Astrophysical Legacy of Guido Barbiellini Amidei

by Roberto Capuzzo Dolcetta

Condens. Matter 2026, 11(2), 22; https://doi.org/10.3390/condmat11020022 - 8 Jun 2026

The development of modern high-energy astrophysics has been deeply intertwined with advances in particle detector technology. Guido Barbiellini Amidei (1943–2024) played a pivotal role in bridging experimental particle physics and astrophysical observation. His scientific career spanned over four decades, from early electron–positron collider [...] Read more.

The development of modern high-energy astrophysics has been deeply intertwined with advances in particle detector technology. Guido Barbiellini Amidei (1943–2024) played a pivotal role in bridging experimental particle physics and astrophysical observation. His scientific career spanned over four decades, from early electron–positron collider experiments at ADONE and LEP (DELPHI) to space-based missions such as AGILE, Fermi, and PAMELA. This memorial paper reviews the evolution of high-energy astrophysics as a detector-driven science, highlighting key domains where Barbiellini left an indelible mark: gamma-ray astronomy, cosmic-ray physics, and antimatter studies. We discuss his personal contributions to silicon tracking, calorimetry, data analysis, and his leadership in international collaborations. The conceptual impact of his interdisciplinary approach is examined, and future perspectives in the observation of the high-energy universe are outlined, recognizing that the path forward is built on the foundations he helped lay. Full article

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

39 pages, 3310 KB

Open AccessReview

MXene-Based Terahertz Metamaterial Biosensors: From Laboratory Simulation to Clinical Application

by Chenxu Jiang, Sitong Li, Junyu Chen, Haoqi Liu, Chenyang Jia, Changlin Yang, Juan Zhang, Jiahao Huang, Xu Xiao and Wenke Xie

Condens. Matter 2026, 11(2), 21; https://doi.org/10.3390/condmat11020021 - 28 May 2026

Terahertz (THz) metamaterial biosensors have emerged as a powerful platform for label-free, non-ionizing biodetection, yet their clinical translation is severely hindered by limited sensitivity, poor anti-interference capability, and a fragmented research chain that rarely extends beyond simulation. Two-dimensional transition metal carbides/nitrides (MXenes) offer [...] Read more.

Terahertz (THz) metamaterial biosensors have emerged as a powerful platform for label-free, non-ionizing biodetection, yet their clinical translation is severely hindered by limited sensitivity, poor anti-interference capability, and a fragmented research chain that rarely extends beyond simulation. Two-dimensional transition metal carbides/nitrides (MXenes) offer a transformative alternative to conventional gold-based metamaterials, providing metal-like high conductivity, abundant surface functional groups for specific biomolecular capture, excellent biocompatibility, and mechanical flexibility. This review systematically examines the recent progress of MXene-based THz metamaterial biosensors, covering structural design strategies, material synergistic system, machine learning-assisted optimization, and performance evaluation metrics. While most studies remain in the simulation stage, a landmark in vivo validation by Yang et al. achieved real-time thrombus monitoring with 94.7% sensitivity and 92.3% specificity, bridging the gap between simulation and clinical application. We identified key bottlenecks hindering clinical translation and propose future directions toward clinically adaptive, full-chain development. This review provides a roadmap for transitioning MXene-based THz biosensors from laboratory simulation to practical point-of-care diagnostics. Full article

(This article belongs to the Special Issue Flexible Matter for Electronics, Photonics, and Energy Conversion)

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32 pages, 738 KB

Open AccessArticle

A Coordination-Based Framework for Superconductivity in Strongly Correlated Systems

by Bin Li

Condens. Matter 2026, 11(2), 20; https://doi.org/10.3390/condmat11020020 - 22 May 2026

High-temperature superconductivity in strongly correlated materials is often accompanied by pseudogap behavior, strange-metal transport, strong phase fluctuations, and reduced superfluid stiffness, particularly in quasi-two-dimensional systems. These features suggest that pairing alone may not determine the onset of global superconductivity. We develop a coordination-based [...] Read more.

High-temperature superconductivity in strongly correlated materials is often accompanied by pseudogap behavior, strange-metal transport, strong phase fluctuations, and reduced superfluid stiffness, particularly in quasi-two-dimensional systems. These features suggest that pairing alone may not determine the onset of global superconductivity. We develop a coordination-based framework in which superconductivity is promoted by the collective organization of internal electronic degrees of freedom coupled to a carrier phase. A minimal lattice model is introduced, combining a U(1) phase sector, an internal coordination field, and an inter-sector coupling. A Landau analysis shows that internal coordination enhances the effective phase stiffness and can destabilize the incoherent state once the coordination amplitude becomes sufficiently large. Monte Carlo simulations of the model confirm that increasing coordination strength enhances phase stiffness and shifts the onset of global coherence to higher temperature. The framework provides a possible organizing interpretation of the separation between pseudogap onset and superconducting coherence, as well as the sensitivity of layered superconductors to reduced dimensionality, competing orders, and vortex-core structure. It is not intended to replace BCS theory, but to extend phase-stiffness-based descriptions to regimes where pairing, local coordination, and global phase coherence are distinct. Full article

(This article belongs to the Section Superconductivity)

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13 pages, 3407 KB

Open AccessArticle

Pseudogap and Condensation in Cuprate Superconductors from NMR Shifts

by Abigail Lee and Jürgen Haase

Condens. Matter 2026, 11(2), 19; https://doi.org/10.3390/condmat11020019 - 16 May 2026

The electronic properties of high-temperature superconducting cuprates are encoded in NMR data. Without microscopic theory, reliable NMR phenomenologies are in demand. Here we make use of the extensive literature data to develop a different understanding of the cuprates from the shifts of the [...] Read more.

The electronic properties of high-temperature superconducting cuprates are encoded in NMR data. Without microscopic theory, reliable NMR phenomenologies are in demand. Here we make use of the extensive literature data to develop a different understanding of the cuprates from the shifts of the

{CuO}_{2}

plane. The Cu shift analysis is based only on the symmetry of the two Cu hyperfine couplings, without assumptions about their size. We use an anisotropic

A_{α}

and isotropic B, as from atomic Cu orbitals, and find two spin components (A- and B-spins) that explain all the shift data. The components differ in size and temperature dependence according to simple rules. Upon doping the cuprates, metallic B-spin appears above a pseudogap temperature, which is shared with the A-spin. Further doping decreases the pseudogap temperature and increases the B-spin, but less so the A-spin. The apparent linear rate of increase in the density of states of the B-spin with doping is nearly threefold above

x = 0.20

, where the pseudogap disappears. The pseudogap temperature is a measure of the coupling between A and B, which suppresses the shifts but not nuclear relaxation. Spin-singlet pairing involves A and B according to three simple condensation rates, which will be discussed. The optimal

T_{c}

demands a special match between A and B. However, the shifts do not simply predict the highest

T_{c}

of all cuprates, in contrast to nuclear relaxation anisotropy and charge sharing between planar Cu and O. Relations to other probes are discussed. Full article

(This article belongs to the Section Superconductivity)

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19 pages, 3296 KB

Open AccessReview

Negative Capacitance Revisited: A Unified Framework Based on Synchronization, Temporal Delay, and Spatial/Quantitative Mismatch

by Yong Sun and Shigeru Kanemitsu

Condens. Matter 2026, 11(2), 18; https://doi.org/10.3390/condmat11020018 - 14 May 2026

Negative capacitance (NC) has been reported across a wide range of physical systems, yet its interpretation has remained fragmented due to the lack of a unified conceptual framework. Existing explanations—spanning ferroelectric free-energy curvature, tunneling transport, plasmonic resonances, and electronic compressibility—have often been treated [...] Read more.

Negative capacitance (NC) has been reported across a wide range of physical systems, yet its interpretation has remained fragmented due to the lack of a unified conceptual framework. Existing explanations—spanning ferroelectric free-energy curvature, tunneling transport, plasmonic resonances, and electronic compressibility—have often been treated as unrelated or even contradictory. This review resolves these inconsistencies by showing that all manifestations of NC arise from non-synchronization between external excitation and internal response. We classify NC into three fundamental categories: temporal mismatch, originating from delays or inertia in charge or polarization dynamics; spatial mismatch, caused by nonuniform field or mode distributions; and quantitative mismatch, resulting from intrinsic parameter reversal such as negative curvature or negative compressibility. Despite their diverse physical origins, these mechanisms share the same mathematical signature (

C_{e f f} = \partial Q / \partial V < 0

). Organizing NC within this unified framework clarifies long-standing ambiguities, connects previously isolated research fields, and establishes a systematic foundation for engineering NC in electronic, photonic, and quantum devices. The framework further highlights tunnel-current-induced NC as a representative single-particle mechanism within the temporal mismatch category, expanding the scope of NC beyond ferroelectricity and collective modes. Overall, this work positions NC not as a singular anomaly but as a universal response class emerging from the interplay between excitation and internal dynamics. Full article

(This article belongs to the Special Issue 10th Anniversary of Condensed Matter: Recent Advances in Condensed Matter Physics)

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21 pages, 798 KB

Open AccessFeature PaperArticle

Impurity-Scattering Assisted Umklapp Scattering as the Origin of Low-Temperature Resistivity in the Normal State of Cuprate Superconductors

by Xingyu Ma, Minghuan Zeng, Huaiming Guo and Shiping Feng

Condens. Matter 2026, 11(2), 17; https://doi.org/10.3390/condmat11020017 - 8 May 2026

The transport experiments reveal that the low-temperature resistivity in the normal state of cuprate superconductors is quadratic in temperature (T-quadratic) in the underdoped pseudogap phase, while it is linear in temperature (T-linear) in the overdoped strange-metal phase; however, the full understanding of these [...] Read more.

The transport experiments reveal that the low-temperature resistivity in the normal state of cuprate superconductors is quadratic in temperature (T-quadratic) in the underdoped pseudogap phase, while it is linear in temperature (T-linear) in the overdoped strange-metal phase; however, the full understanding of these different behaviors is still a challenging issue. Here starting from the microscopic electronic structure of cuprate superconductors, the low-temperature resistivity in the normal state is investigated from the underdoped pseudogap phase to the overdoped strange-metal phase. It is shown that the mechanism requires both the impurity scattering and the umklapp scattering: the impurity scattering is needed to restrict the modification of the distribution function to at and around the antinodal region, while the impurity-scattering assisted umklapp scattering from a spin excitation is at the heart of the behavior in the low-temperature resistivity, where the doping dependence of the temperature scale exists, and presents a similar behavior of the antinodal spin pseudogap crossover temperature. In the low-temperature region above the temperature scale in the overdoped strange-metal phase, the resistivity is T-linear; however, in the low-temperature region below the temperature scale in the underdoped pseudogap phase, the opening of the spin pseudogap lowers the spin excitation density of states at and around the antinodal region, which reduces the strength of the electron umklapp scattering from a spin excitation associated with the antinode, and thus leads to a T-quadratic behavior of the resistivity. Full article

(This article belongs to the Special Issue Superstripes Physics, 4th Edition)

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19 pages, 4072 KB

Open AccessArticle

Josephson Interferometry of Helical Phases in Superconducting Heterostructures

by Paulo J. F. Cavalcanti, Jérôme Cayssol and Alexander I. Buzdin

Condens. Matter 2026, 11(2), 16; https://doi.org/10.3390/condmat11020016 - 29 Apr 2026

We suggest Josephson interferometry as a quantitative probe of spin–orbit-driven phenomena in superconducting heterostructures. Two distinct mechanisms are analyzed: (i) intrinsic helical superconductivity, producing asymmetric Fraunhofer patterns with lobe deformations and field-reversal asymmetry, and (ii) emergent interfacial magnetism in ferromagnet–superconductor hybrids, where Rashba [...] Read more.

We suggest Josephson interferometry as a quantitative probe of spin–orbit-driven phenomena in superconducting heterostructures. Two distinct mechanisms are analyzed: (i) intrinsic helical superconductivity, producing asymmetric Fraunhofer patterns with lobe deformations and field-reversal asymmetry, and (ii) emergent interfacial magnetism in ferromagnet–superconductor hybrids, where Rashba spin–orbit coupling generates spontaneous fields that rigidly shift the interference fringes. The predicted signatures—flux-shifted interference minima, anisotropic critical current suppression, and angle-dependent pattern distortions—provide direct experimental access to finite-momentum pairing and interface-localized fields via standard Josephson current measurements. Full article

(This article belongs to the Special Issue 10th Anniversary of Condensed Matter: Recent Advances in Condensed Matter Physics)

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11 pages, 1458 KB

Open AccessOpinion

Lasting Aftermaths of the First Incitement for High-Temperature Superconductivity

by Serguei Brazovskii and Natasha Kirova

Condens. Matter 2026, 11(2), 15; https://doi.org/10.3390/condmat11020015 - 27 Apr 2026

Six decades ago, the scientist from Stanford University, W.P. Little, announced a crusade to search for superconductivity, assumed to be heat-resistant in organic materials. Although such an ambitious goal was never realized in practice, this proposal gave rise to the entire ecosystem of [...] Read more.

Six decades ago, the scientist from Stanford University, W.P. Little, announced a crusade to search for superconductivity, assumed to be heat-resistant in organic materials. Although such an ambitious goal was never realized in practice, this proposal gave rise to the entire ecosystem of studies on “synthetic metals,” creating a diverse community of material, experimental, and theoretical activities in low-dimensional electronic systems. We shall briefly review some key steps in this history, examine its main branches, and recall the consequences that remain on the agenda today. Particularly, we shall focus on a phenomenon of electronic ferroelectricity, whose roots can be found in the suggestion of a would-be superconducting polymer. Full article

(This article belongs to the Special Issue Superstripes Physics, 4th Edition)

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10 pages, 1826 KB

Open AccessArticle

Liquid-Precursor-Mediated CVD Synthesis of WSe₂

by Krastyo Buchkov, Peter Rafailov, Nikolay Minev, Vladimira Videva, Ivalina Avramova, Velichka Strijkova, Todor Lukanov, Dimitre Dimitrov and Vera Marinova

Condens. Matter 2026, 11(2), 14; https://doi.org/10.3390/condmat11020014 - 23 Apr 2026

The present study focuses on liquid-precursor-mediated chemical vapor deposition (under ambient pressure and moderate temperature range) of WSe₂ on sapphire using ammonium meta-tungstate and sodium cholate. The investigation provides additional results and information for the WSe₂ cluster formations on sapphire as [...] Read more.

The present study focuses on liquid-precursor-mediated chemical vapor deposition (under ambient pressure and moderate temperature range) of WSe₂ on sapphire using ammonium meta-tungstate and sodium cholate. The investigation provides additional results and information for the WSe₂ cluster formations on sapphire as an extension of our previous study, especially based on structural, chemical and morphological characterization of the observed largest and predominant polygonal WSe₂ domains whose lateral size can reach several hundreds of micrometers. In addition, highly symmetrical shapes were also observed. The Raman spectroscopy and atomic force microscopy identified the formation of both mono- and multilayered WSe₂. Moreover, the Raman spectrum analysis shows a complex peak structure with unusual splitting effects in the second-order modes marking strong activity of excitonic-resonance processes. Full article

(This article belongs to the Section Physics of Materials)

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15 pages, 4625 KB

Open AccessArticle

Magnetic Nanocomposite-Driven Harvesting of Chlorella vulgaris: Enhancing Microalgal Biomass Recovery Using Fe₃O₄ and Fe₃O₄@PEG Nanoparticles

by Lady Johana Endo Aguilar, Indry Milena Saavedra Gaona, Carlos Arturo Parra Vargas, Jahaziel Amaya, Jaime Ernesto Vargas and Daniel Llamosa Pérez

Condens. Matter 2026, 11(2), 13; https://doi.org/10.3390/condmat11020013 - 20 Apr 2026

This study investigates magnetic harvesting of Chlorella vulgaris cultivated under saline and wastewater conditions using Fe₃O₄ and polyethylene-glycol-coated Fe₃O₄ (Fe₃O₄@PEG) nanoparticles synthesized by ultrasound-assisted coprecipitation. TEM showed agglomerated, quasi-spherical particles with mean diameters [...] Read more.

This study investigates magnetic harvesting of Chlorella vulgaris cultivated under saline and wastewater conditions using Fe₃O₄ and polyethylene-glycol-coated Fe₃O₄ (Fe₃O₄@PEG) nanoparticles synthesized by ultrasound-assisted coprecipitation. TEM showed agglomerated, quasi-spherical particles with mean diameters of 13 ± 1 nm (Fe₃O₄) and 15 ± 1 nm (Fe₃O₄@PEG). FTIR confirmed the Fe–O vibrational bands of magnetite and the characteristic PEG vibrations in the coated sample. VSM measurements indicated superparamagnetic behavior, with saturation magnetizations of 72.74 emu/g for Fe₃O₄ and 32.25 emu/g for Fe₃O₄@PEG. SEM–EDX of native and functionalized cells verified nanoparticle attachment on the algal surface. Magnetic separation experiments (OD684) showed a decrease in supernatant absorbance with increasing nanoparticle dose, consistent with biomass removal; the PEG-coated system showed a lower apparent biomass concentration after functionalization. Full article

(This article belongs to the Section Magnetism)

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16 pages, 2287 KB

Open AccessArticle

Phase Transformation and Magnetic Properties of Rapidly Solidified Mn-Al Alloys

by Marco A. Camacho-Peralta, Israel Betancourt and Jose T. Elizalde-Galindo

Condens. Matter 2026, 11(2), 12; https://doi.org/10.3390/condmat11020012 - 17 Apr 2026

Mn₅₄Al₄₆ alloys with τ-phase as their main component were successfully obtained in a reproducible processing window combining melt-spinning, annealing at intermediate temperatures (450 °C) and low-energy milling. The complete ε → τ phase transformation was driven by thermal decomposition of [...] Read more.

Mn₅₄Al₄₆ alloys with τ-phase as their main component were successfully obtained in a reproducible processing window combining melt-spinning, annealing at intermediate temperatures (450 °C) and low-energy milling. The complete ε → τ phase transformation was driven by thermal decomposition of ε-phase and favored by high grain boundary density inherent to the melt-spun microstructure. An improved magnetic response of the melt-spun Mn₅₄Al₄₆ alloys was observed, as they exhibited saturation magnetization values between 80 and 90 emu/g, together with intrinsic coercivities around 2000 Oe and Curie temperatures between 640 and 648 K. Significant coercivity enhancement over 6000 Oe was predicted, by means of micromagnetic calculations, for alloys with grain size refinement below 100 nm. The efficient, single-step experimental phase transformation with no additional stabilizers for the τ-phase was explained in terms of microstructural features, whereas magnetic enhancement was attributed to lattice distortions promoted by the milling process. This integrated approach introduces a pathway to achieve τ-phase Mn-Al with tunable magnetic performance useful for applications. Full article

(This article belongs to the Section Magnetism)

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17 pages, 5307 KB

Open AccessArticle

Impact of Synthesis Temperature on the Structural, Electronic Structural, Optical, Magnetic, and Electrochemical Properties of SmFeO₃ Nanoparticles

by Sakshi Khandal, Preksha Gagneja, Manas Nasit, Sameer Saharan, Sarita Khaturia, Pratibha Sharma, Sujata Kumari, P. A. Alvi, Naveen Yadav, Bon-Heun Koo, Shalendra Kumar and Kavita Kumari

Condens. Matter 2026, 11(2), 11; https://doi.org/10.3390/condmat11020011 - 31 Mar 2026

Cited by 1

The multifunctional attributes of SmFeO₃ make it a promising candidate for the current diverse technological applications. Therefore, in this work, we investigated the effect of synthesis temperature on the magnetic, optical and electrochemical properties of SmFeO₃ nanoparticles at room temperature (SFO-RT) [...] Read more.

The multifunctional attributes of SmFeO₃ make it a promising candidate for the current diverse technological applications. Therefore, in this work, we investigated the effect of synthesis temperature on the magnetic, optical and electrochemical properties of SmFeO₃ nanoparticles at room temperature (SFO-RT) and 50 °C (SFO-50) when prepared through the co-precipitation method. The XRD analysis revealed two distinct phases: SmFeO₃ and Sm₂O₃ as secondary with SmFeO₃ emerging as the primary phase (88–93%). The FESEM images showed the amalgamated morphology of the nanoparticles indicating the enhanced thermal kinetics of the solution which not only limited the particle growth but also facilitated their coalition. The band gap energy was found to be 2.2 and 2.3 eV for SFO-RT and SFO-50, respectively, while the values of saturation magnetization noted were 2.14 and 1.53 emu/g for SFO-RT and SFO-50, respectively. The XPS analysis revealed Sm to be in a +3 oxidation state, while Fe was in a mixed (+3/+2) oxidation state showing an increase in the ionic concentration in SFO-50. From the electrochemical measurements, the highest specific capacitance was observed for SFO-50 (65.8 F/g) as compared to SFO-RT (49.3 F/g). The results indicate a clear effect of synthesis temperature on the properties of SmFeO₃. Here, two factors played a prominent role: one was the morphology, shaped through the particle growth, and the other was the secondary phase. The decrease in the size of the agglomerated particles and phase fraction of the secondary phase brought about necessary changes in the structural attributes to reduce the saturation magnetization and enhance the specific capacitance of SFO-50. Overall, this study shows that the synthesis temperature affects the crystalline structure and phase fractions leading to the modulation of electronic structure, band gap, magnetic interactions and specific capacitance. Full article

(This article belongs to the Special Issue Synergistic Electrochemical and Magnetic Behavior in Nanocomposite Materials)

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22 pages, 1738 KB

Open AccessReview

Bridging Quantum Capacitance and Experimental Electrochemical Performance in 2D Materials for Supercapacitors: From Density of States to Device-Level Interpretation

by Maria C. Barrero-Moreno, Abraham Méndez-Reséndiz, Juan C. Carrillo-Rodriguez and Andrés M. Garay-Tapia

Condens. Matter 2026, 11(1), 10; https://doi.org/10.3390/condmat11010010 - 21 Mar 2026

Two-dimensional (2D) materials, particularly MXenes and transition metal dichalcogenides (TMDs), have attracted intense interest as supercapacitor electrodes due to their high surface area and tunable electronic structure. However, large discrepancies persist between the quantum capacitance values predicted by density functional theory (DFT) calculations [...] Read more.

Two-dimensional (2D) materials, particularly MXenes and transition metal dichalcogenides (TMDs), have attracted intense interest as supercapacitor electrodes due to their high surface area and tunable electronic structure. However, large discrepancies persist between the quantum capacitance values predicted by density functional theory (DFT) calculations and experimentally measured gravimetric capacitances. In this review, we critically analyze DFT methodologies, surface models, normalization strategies, and electrochemical characterization protocols, and compile an extensive dataset of reported MXene and TMD systems to quantify the degree of experimental–theoretical agreement. We show that MXenes typically achieve less than 20% of their predicted capacitance because of restacking, surface terminations, and limited ion accessibility, whereas TMDs exhibit substantially better correspondence, often approaching or exceeding 70% of theoretical values. These results indicate that the theoretical capacitance predicted by DFT is primarily determined by the electronic structure of the material, which defines the upper limit of charge storage, whereas the experimentally achieved capacitance is largely controlled by morphological factors, surface chemistry, and electrode architecture that limit ion accessibility. Full article

(This article belongs to the Special Issue Flexible Matter for Electronics, Photonics, and Energy Conversion)

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11 pages, 516 KB

Open AccessArticle

Two-Dimensional Tunable Reactance Element Free from Electromagnetic Coupling

by Yong Sun and Shigeru Kanemitsu

Condens. Matter 2026, 11(1), 9; https://doi.org/10.3390/condmat11010009 - 2 Mar 2026

Cited by 1

A capacitor modeled as a parallel combination of a resistance (

R

) and a capacitance (

C

) exhibits three distinct operating regimes when both parameters depend on the applied voltage (V): a positive-capacitance regime ( [...] Read more.

A capacitor modeled as a parallel combination of a resistance (

R

) and a capacitance (

C

) exhibits three distinct operating regimes when both parameters depend on the applied voltage (V): a positive-capacitance regime (

d R / R > d V / V

), an Ohmic regime (

d R / R = d V / V

), and a negative-capacitance regime (

d R / R < d V / V

). In the limit (

R \to \infty

), the device behaves as a conventional permittivity-based capacitor, whereas in the limit (

R \to 0

), negative capacitance emerges due to nonlinear current–voltage characteristics. To verify this mechanism, we fabricated nanometer-spaced two-electrode structures using multi-walled carbon nanotubes (MWCNTs) and Si crystals. The measurements confirmed negative capacitance consistent with theoretical predictions. Unlike ferroelectric negative capacitance, the effect demonstrated here arises solely from the nonlinear I–V characteristics at the electrode interfaces, without involving any ferroelectric polarization dynamics. This negative capacitance can be interpreted as an equivalent inductance, enabling a two-dimensional tunable reactance element (TDTRE) that operates without electromagnetic coupling and is compatible with conventional IC technologies. Full article

(This article belongs to the Section Physics of Materials)

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11 pages, 5872 KB

Open AccessFeature PaperArticle

Measurements of Electronic Band Structure in CeCoGe₃ by Angle-Resolved Photoemission Spectroscopy

by Robert Prater, Mingkun Chen, Matthew Staab, Sudheer Sreedhar, Journey Byland, Zihao Shen, Sergey Y. Savrasov, Valentin Taufour, Vsevolod Ivanov and Inna Vishik

Condens. Matter 2026, 11(1), 8; https://doi.org/10.3390/condmat11010008 - 25 Feb 2026

In this paper, we present a comprehensive study of the electronic structure of CeCoGe₃ throughout the entire Brillouin zone in the non-magnetic regime using angle-resolved photoemission spectroscopy (ARPES). The electronic structure agrees in large part with first principles calculations, including predicted topological [...] Read more.

In this paper, we present a comprehensive study of the electronic structure of CeCoGe₃ throughout the entire Brillouin zone in the non-magnetic regime using angle-resolved photoemission spectroscopy (ARPES). The electronic structure agrees in large part with first principles calculations, including predicted topological nodal lines. Two new features in the band structure are also observed, namely a surface state and folded bands, the latter of which is argued to originate from a unit cell reconstruction. Full article

(This article belongs to the Special Issue Topological and Quantum Materials for Energy and Information: Spectroscopy and Computation Approaches)

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20 pages, 10183 KB

Open AccessFeature PaperArticle

Laser-Spot Step-Heating Thermography for Non-Destructive Evaluation of Thermal Diffusivity in Apples

by Ginevra Lalle, Alessandro Maurizi, Anna Maria Giusti, Grigore Leahu, Gianmario Cesarini, Emilija Petronijevic, Alesandro Belardini and Roberto Li Voti

Condens. Matter 2026, 11(1), 7; https://doi.org/10.3390/condmat11010007 - 18 Feb 2026

In this work, thermal imaging is employed to study the opto-thermal response of apples (Malus domestica Borkh.), assessing their post-harvest evolution through the estimation of thermal diffusivity. A non-destructive experimental procedure based on mid-wave infrared (MWIR) thermal camera (3–5 µm) and localized heating [...] Read more.

In this work, thermal imaging is employed to study the opto-thermal response of apples (Malus domestica Borkh.), assessing their post-harvest evolution through the estimation of thermal diffusivity. A non-destructive experimental procedure based on mid-wave infrared (MWIR) thermal camera (3–5 µm) and localized heating with a visible laser is developed, enabling spatially and temporally resolved surface temperature measurements. Temperature fields are recorded at different time points and radial distances from the heated spot. A theoretical model based on Fourier thermal diffusion equation is formulated to describe the spatio-temporal evolution of surface temperature. After validation on a reference sample, the method is applied to Golden and Red Delicious apples over a 28-day storage period at room temperature. Red Delicious apple exhibits higher mean diffusivity values without significant temporal changes, whereas a progressive increase in diffusivity is observed for Golden Delicious apples. These results show that thermal diffusivity is sensitive to post-harvest physiological changes in apple tissue and may be associated with intrinsic properties such as tissue density and water content. By relating laser-induced temperature fields to the estimation of thermal diffusivity, this approach enables the non-destructive, quantitative assessment of thermal diffusivity, showing potential for fruit maturity and quality assessment, which are of high importance in agri-food monitoring applications. Full article

(This article belongs to the Section Spectroscopy and Imaging in Condensed Matter)

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21 pages, 3379 KB

Open AccessArticle

Insights into Neutral vs. Deprotonated Phenol Adsorption on Graphene Oxide

by Jeton Halili, Kledi Xhaxhiu, Nensi Isak, Makfire Sadiku, Arianit Reka, Muhamed Farruku and Avni Berisha

Condens. Matter 2026, 11(1), 6; https://doi.org/10.3390/condmat11010006 - 6 Feb 2026

Cited by 1

Water pollution from phenols remains a critical concern due to their persistence, toxicity, and industrial prevalence. Graphene oxide (GOx), with its functional groups and large surface area, offers strong adsorption potential. Using density functional theory (DFT), reduced density gradient (RDG), and quantitative structure–activity [...] Read more.

Water pollution from phenols remains a critical concern due to their persistence, toxicity, and industrial prevalence. Graphene oxide (GOx), with its functional groups and large surface area, offers strong adsorption potential. Using density functional theory (DFT), reduced density gradient (RDG), and quantitative structure–activity relationship (QSAR), we examined how protonation and substituents influence phenol adsorption. Deprotonated phenolates bind more strongly to GO than neutral species via electrostatics and H-bonding. Substituents alter affinity: halogens enhance it, bulky alkyls hinder it, and nitro groups show electron-withdrawing effects. Bisphenolate A displayed multidentate binding. QSAR models reproduced DFT energies with R² > 0.99, enabling fast prediction. These results highlight how pH speciation and substituents govern adsorption on GO, guiding the design of efficient water treatment materials. Full article

(This article belongs to the Special Issue Selected Papers from the 3-Day International Conference on Materials Science (3D-ICOMAS))

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Open AccessFeature PaperArticle

Two-Carrier Description of Cuprate Superconductors from NMR

by Daniel Bandur, Abigail Lee, Jakob Nachtigal, Stefan Tsankov and Jürgen Haase

Condens. Matter 2026, 11(1), 5; https://doi.org/10.3390/condmat11010005 - 5 Feb 2026

Cited by 1

Cuprates currently hold the record for the highest temperature superconductivity at ambient pressure, but the microscopic understanding of these materials remains elusive. Here, we utilize nuclear magnetic resonance (NMR) data of planar oxygen and copper from essentially all hole-doped cuprates to provide a [...] Read more.

Cuprates currently hold the record for the highest temperature superconductivity at ambient pressure, but the microscopic understanding of these materials remains elusive. Here, we utilize nuclear magnetic resonance (NMR) data of planar oxygen and copper from essentially all hole-doped cuprates to provide a universal phenomenology relating the NMR spin shifts, which measure the electronic spin polarization at a given nucleus, with the superconducting dome and maximum critical temperature. There appear to be two separate contributions to the spin shift in planar copper, only one of which is seen at the oxygen site, and we associate them with two different types of carriers. Upon disentangling these two components, their relative size is shown to correlate not only with the doping dependence of the superconducting dome but also with the variation in maximum superconducting critical temperature,

T_{c, \max}

, between different families. One of these components is independent of family and resides in the hybridized planar orbitals of Cu and O. The second component, in contrast, is predominately isotropic and encodes the differences between the families. It is thus related to the charge transfer gap and planar hole sharing. Our findings offer universal insight which should prove useful in the continuing development of a comprehensive theory of the cuprates, as well as an indication of how it may be possible to engineer materials with higher critical temperatures. Full article

(This article belongs to the Special Issue Superstripes Physics, 4th Edition)

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12 pages, 2292 KB

Open AccessArticle

Electron Correlation and High-Temperature Superconductivity

by Takeshi Egami

Condens. Matter 2026, 11(1), 4; https://doi.org/10.3390/condmat11010004 - 30 Jan 2026

Strong electron correlation plays a central role in the high-temperature superconductivity (HTSC) of cuprates. However, to date, research has focused only on its role in spin dynamics and related effects, even though it is becoming increasingly clear that spin alone may not be [...] Read more.

Strong electron correlation plays a central role in the high-temperature superconductivity (HTSC) of cuprates. However, to date, research has focused only on its role in spin dynamics and related effects, even though it is becoming increasingly clear that spin alone may not be sufficient to create HTSC. Here, we discuss a possible role of electron correlation in the Bose–Einstein condensation (BEC) of Cooper pairs. Recently, we succeeded in observing dynamic electron correlation via inelastic X-ray scattering through results presented in real space. We discovered that electron correlations are strongly modified in the plasmon, proving that electron dynamics significantly affect electron correlation. Earlier, we found that in ⁴He, the atom–atom distance in the BE condensate is 10% longer than that in the non-condensate. These results suggest the possibility that the reduction in electron-repulsion energy upon BEC is driving T_c to high values. Thus, electron correlation itself could be the origin of the HTSC phenomenon. Full article

(This article belongs to the Special Issue Superstripes Physics, 4th Edition)

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