Condensed Matter

15 pages, 4030 KiB

Open AccessArticle

The Defect Charge Effect on Magnetic Anisotropy Energy and Dzyaloshinskii–Moriya Interaction of the I Vacancy and 3d Transition Metal Co-Doped Monolayer CrI₃

by Guangtian Ji, Qingqing Yang, Kun Zhang, Jueming Yang, Guixian Ge and Wentao Wang

Condens. Matter 2025, 10(2), 29; https://doi.org/10.3390/condmat10020029 - 14 May 2025

Abstract

Recently, significant effort has been devoted to enhancing magnetic anisotropy energy (MAE) and the Dzyaloshinskii–Moriya interaction (DMI) in two-dimensional (2D) ferromagnetic materials through various tuning approaches. Among these methods, defect engineering is one of the most effective strategies. However, the influence of these [...] Read more.

Recently, significant effort has been devoted to enhancing magnetic anisotropy energy (MAE) and the Dzyaloshinskii–Moriya interaction (DMI) in two-dimensional (2D) ferromagnetic materials through various tuning approaches. Among these methods, defect engineering is one of the most effective strategies. However, the influence of these charged defects on the MAE and DMI is unclear. Therefore, we systematically investigate the defect effect on the MAE and DMI of I vacancy-doped (v_I-CrI₃), 3d-transition-metal-doped (TM = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) (3d-TM_i@CrI₃), and v_I-TM co-doped (3d-TM_i@v_I-CrI₃) monolayer CrI₃ using first-principles calculations. Our results indicate that Cr-rich conditions can promote the defect formation of v_I-CrI₃, 3d-TM_i@CrI₃, and 3d-TM_i@v_I-CrI₃ systems and demonstrate that 49 types of charged systems are stable. Among these systems, the Cu_i@v_I-CrI₃ in the +1 charge state (Cu_i^•@v_I-CrI₃) system has a smaller defect formation energy, exhibiting a large MAE exceeding 30 meV, and the ratio (D/J) of the antisymmetric magnetic exchange parameter (D) to the Heisenberg exchange parameter (J) reaches 1.04. The large MAE originates from the transition from single-ion anisotropy (SIA) to covalent interaction anisotropy (CIA) due to the coupling variation between the p_y and p_x orbitals of I atoms near the Fermi level caused by charge states. The enhancement of the DMI is due to the electrostatic potential differences between the I-top and I-bottom layers, which are conducive to forming stable chiral spin textures. This study provides insight into the defect charge state modulating the magnetism of 2D magnetic materials. Full article

► Show Figures

Figure 1

8 pages, 1555 KiB

Open AccessArticle

Effect of Annealing Time of GaN Buffer Layer on Curvature and Wavelength Uniformity of Epitaxial Wafer

by Huanyou Wang, Guangqi Xie and Yingying Zhan

Condens. Matter 2025, 10(2), 28; https://doi.org/10.3390/condmat10020028 - 1 May 2025

Abstract

In this study, the curvature changes of an unintentionally doped GaN end and third quantum well were observed in situ when the annealing times of a GaN buffer layer were 40 s, 50 s and 55 s, respectively. When the annealing time was [...] Read more.

In this study, the curvature changes of an unintentionally doped GaN end and third quantum well were observed in situ when the annealing times of a GaN buffer layer were 40 s, 50 s and 55 s, respectively. When the annealing time was increased from 40 s to 50 s, the concave curvature of the unintentionally doped GaN end and the third quantum well became smaller. When the annealing time was increased to 55 s, there was no significant change in curvature. These curvature changes are related to the relaxation of the stress in the epitaxial wafer with different annealing times. With the increase in buffer annealing time, the compressive stress and warpage decreased gradually, and the photoluminescence wavelength of the sample became longer. Meanwhile, the standard deviation yield of the dominant wavelength was increased by 5.46%, and the wavelength yield was increased by 19.45% when the annealing time was changed from 40 s to 50 s. Full article

► Show Figures

Figure 1

13 pages, 751 KiB

Open AccessArticle

Effect of t_2g-Correlations and Doping in CrSBr Ferromagnetic Semiconductor

by Luis Craco and Sabrina Silva Carara

Condens. Matter 2025, 10(2), 27; https://doi.org/10.3390/condmat10020027 - 28 Apr 2025

Abstract

We perform a comprehensive analysis of the correlated electronic structure reconstruction of the ferromagnetic CrSBr van der Waals (vdW) bulk crystal. Using generalized gradient approximation combined with dynamical mean-field theory, we show the minor role played by multi-orbital electron–electron interactions in semiconducting CrSBr. [...] Read more.

We perform a comprehensive analysis of the correlated electronic structure reconstruction of the ferromagnetic CrSBr van der Waals (vdW) bulk crystal. Using generalized gradient approximation combined with dynamical mean-field theory, we show the minor role played by multi-orbital electron–electron interactions in semiconducting CrSBr. Our study is relevant to understanding the electronic structure within the

{C r}^{3 +}

oxidation state with strongly spin-polarized

t_{2 g}

orbitals and should be applicable to other ferromagnetic vdW materials from bulk down to the low-dimensional limit. This work is relevant for understanding orbital and spin selectivity and its link to the memristor current–voltage characteristic of CrSBr for future neuromorphic computing. Full article

(This article belongs to the Section Condensed Matter Theory)

► Show Figures

Figure 1

18 pages, 23429 KiB

Open AccessArticle

Synthesis of PTh/PEDOT Films into FTO Substrate by Electrodeposition, for Energy Storage Systems

by Daniel Alejandro Vázquez-Loredo, Ulises Páramo-García, Luis Alejandro Macclesh Del Pino-Pérez, Nohra Violeta Gallardo-Rivas, Ricardo García-Alamilla and Diana Lucia Campa-Guevara

Condens. Matter 2025, 10(2), 26; https://doi.org/10.3390/condmat10020026 - 27 Apr 2025

Abstract

Thin films of monomeric species polythiophene (PTh), poly-(3,4-ethylenedioxythiophene) (PEDOT), and the copolymer PTh/PEDOT were prepared through electropolymerization and deposited above fluorine-doped tin oxide (FTO) substrates. The functional groups of the monomeric species (PTh, PEDOT) and polymeric species (PTh/PEDOT) were characterized by Fourier-transform infrared [...] Read more.

Thin films of monomeric species polythiophene (PTh), poly-(3,4-ethylenedioxythiophene) (PEDOT), and the copolymer PTh/PEDOT were prepared through electropolymerization and deposited above fluorine-doped tin oxide (FTO) substrates. The functional groups of the monomeric species (PTh, PEDOT) and polymeric species (PTh/PEDOT) were characterized by Fourier-transform infrared spectroscopy, while morphological properties were evaluated using scanning electron microscopy, optical microscopy, and atomic force microscopy. The analysis showed that monomers films exhibited less material deposition; otherwise, the copolymer PTh/PEDOT showed better deposition on substrate. In addition, the electrochemical characterization showed that the materials that resulted from copolymerization presented an improvement in electrochemical properties relating to monomer properties. The effect of overoxidation of the monomers applied during the electropolymerization process is also known. Full article

(This article belongs to the Section Surface and Interfaces)

► Show Figures

Figure 1

3 pages, 145 KiB

Open AccessEditorial

Novel Radiation Facilities Based on Plasma Acceleration: The Future of Free Electron Lasers

by Marcello Coreno, Massimo Ferrario, Augusto Marcelli and Francesco Stellato

Condens. Matter 2025, 10(2), 25; https://doi.org/10.3390/condmat10020025 - 27 Apr 2025

Abstract

Exploiting acceleration gradients that are up to three orders of magnitude higher than those achievable using conventional radiofrequency-based devices, plasma-based devices promise a revolution in particle acceleration, enabling particles to reach high energies over much shorter distances than existing accelerators [...] Full article

(This article belongs to the Special Issue Experimental Ideas for Novel FEL Facilities Based on Plasma Acceleration)

3 pages, 123 KiB

Open AccessEditorial

In-Depth Experimental and Computational Studies on Rechargeable Battery Materials

by Jan Kuriplach and Rolando Saniz

Condens. Matter 2025, 10(2), 24; https://doi.org/10.3390/condmat10020024 - 25 Apr 2025

Abstract

Judging by the number of downloads and citations, the topics covered by the Special Issue “Rechargeable Batteries Studied Using Advanced Spectroscopic and Computational Techniques I” [...] Full article

(This article belongs to the Special Issue Rechargeable Batteries Studied Using Advanced Spectroscopic and Computational Techniques II)

8 pages, 512 KiB

Open AccessArticle

Energy Structure of Yb³⁺-Yb³⁺ Paired Center in LiNbO₃ Crystal

by Gagik Demirkhanyan, Narine Babajanyan, Ninel Kokanyan, Michel Aillerie, Marco Bazzan and Edvard Kokanyan

Condens. Matter 2025, 10(2), 23; https://doi.org/10.3390/condmat10020023 - 25 Apr 2025

Abstract

Within the framework of Dexter’s theory, we calculate the energies of the Stark levels of Yb³⁺-Yb³⁺ paired centers in lithium niobate doped with Yb³⁺ ions (LiNbO₃:Yb³⁺) crystal, considering the interaction of optical electrons of ytterbium [...] Read more.

Within the framework of Dexter’s theory, we calculate the energies of the Stark levels of Yb³⁺-Yb³⁺ paired centers in lithium niobate doped with Yb³⁺ ions (LiNbO₃:Yb³⁺) crystal, considering the interaction of optical electrons of ytterbium ions forming the paired center. The calculated Stark level energies are shown to correspond well with the observed cooperative luminescence wavelengths. Full article

► Show Figures

Figure 1

24 pages, 3710 KiB

Open AccessReview

The Laser Powder Bed Fusion of Nd₂Fe₁₄B Permanent Magnets: The State of the Art

by Ivan Pelevin, Maria Lyange, Leonid Fedorenko, Stanislav Chernyshikhin and Irina Tereshina

Condens. Matter 2025, 10(2), 22; https://doi.org/10.3390/condmat10020022 - 24 Apr 2025

Abstract

In recent years, significant effort was made to make the 3D printing of fully dense rare-earth permanent magnets a reality. Since suitable Nd₂Fe₁₄B-based initial powder material became available, additive manufacturing implementation spread widely, which led to many studies being [...] Read more.

In recent years, significant effort was made to make the 3D printing of fully dense rare-earth permanent magnets a reality. Since suitable Nd₂Fe₁₄B-based initial powder material became available, additive manufacturing implementation spread widely, which led to many studies being focused on using this material in 3D printing. This study shows the principal possibilities of the synthesis of Nd-Fe-B magnets by means of the laser powder bed fusion technique; moreover, this study shows significant progress in increasing their magnetic properties. This progress was made possible by different approaches, such as 3D-printing process optimization, the addition of a second phase (a low-melting eutectic) into the initial powder, the tuning of the main phase’s composition, and exploring different scanning strategies. However, the current level of material magnetic properties obtained via laser powder bed fusion is still far from that of magnets produced by using conventional powder metallurgy methods. The present review aims to capture the current state-of-the-art trials and highlight the main challenges. Full article

(This article belongs to the Section Magnetism)

► Show Figures

Figure 1

29 pages, 10332 KiB

Open AccessReview

Basic Aspects of Ferroelectricity Induced by Noncollinear Alignment of Spins

by I. V. Solovyev

Condens. Matter 2025, 10(2), 21; https://doi.org/10.3390/condmat10020021 - 11 Apr 2025

Abstract

Basic principles of ferroelectric activity induced by the noncollinear alignment of spins are reviewed. There is a fundamental reason why the inversion symmetry can be broken by certain magnetic order. This situation occurs when the magnetic order simultaneously involves ferromagnetic (

F

) [...] Read more.

Basic principles of ferroelectric activity induced by the noncollinear alignment of spins are reviewed. There is a fundamental reason why the inversion symmetry can be broken by certain magnetic order. This situation occurs when the magnetic order simultaneously involves ferromagnetic (

F

) and antiferromagnetic (

A

) counterparts, transforming under the spatial inversion

I

and time reversal

T

as

I F = F

and

IT A = A

, respectively. The incompatibility of these two conditions results in breaking the inversion symmetry, which manifests itself in the electric polarization

\vec{P}

. The noncollinear alignment of spins is one of examples of such coexistence of

F

and

A

. This coexistence principle imposes a constraint on possible dependencies of

\vec{P}

on the directions of spins, which can include only “antisymmetric coupling” in the bond,

{\vec{P}}_{i j} \cdot [e_{i} \times e_{j}]

, and “single-ion anisotropy”,

e_{i} \cdot

\vec{Π}

e_{i}

. Microscopically,

{\vec{P}}_{i j}

can be evaluated in the framework of superexchange theory. For the single Kramers doublet, this theory yields

{\vec{P}}_{i j} \sim {\vec{r}}_{i j}^{}

, where

{\vec{r}}_{i j}^{}

is the spin-dependent part of the position operator induced by the relativistic spin-orbit coupling.

{\vec{r}}_{i j}^{}

remains invariant under spatial inversion, providing the microscopic reason why noncollinear alignment of spins can induce

\vec{P}

even in centrosymmetric crystals. The symmetry properties of

{\vec{r}}_{i j}^{}

can be rationalized from the viewpoint of symmetry of Kramers states. Particularly, the commonly used Katsura–Nagaosa–Balatsky (KNB) rule

\vec{P} \propto {\vec{ϵ}}_{j i} \times [e_{i} \times e_{j}]

(

{\vec{ϵ}}_{j i}

being the direction of the bond

i j

) can be justified only for relatively high symmetry of the bonds. The single-ion anisotropy vanishes for the spin

\frac{1}{2}

or if magnetic ions are located in inversion centers, thus severely restricting the applicability of this microscopic mechanism. The properties of multiferroic materials are reconsidered from the viewpoint of these principles. A particular attention is paid to complications caused by possible deviations from the KNB rule. Full article

► Show Figures

Figure 1

14 pages, 991 KiB

Open AccessReview

Emergent Magnetic Monopoles in Quantum Matter

by Maria Cristina Diamantini

Condens. Matter 2025, 10(2), 20; https://doi.org/10.3390/condmat10020020 - 1 Apr 2025

Abstract

Magnetic monopoles, though elusive as elementary particles, emerge as quantum excitations in granular quantum materials. Under certain conditions, they can undergo Bose condensation, leading to the formation of a novel state of matter known as the superinsulator. In this state, charge carriers, Cooper [...] Read more.

Magnetic monopoles, though elusive as elementary particles, emerge as quantum excitations in granular quantum materials. Under certain conditions, they can undergo Bose condensation, leading to the formation of a novel state of matter known as the superinsulator. In this state, charge carriers, Cooper pairs and anti-Cooper pairs, are bound together by an electric flux string, forming neutral electric pions. This confinement mechanism results in an infinite resistance that persists even at finite temperatures. Superinsulators behave, thus, as dual superconductors. Full article

(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)

► Show Figures

Figure 1

16 pages, 5365 KiB

Open AccessArticle

Kinetics of Thickness Growth of Silicon Films During Pulsed Magnetron Sputtering Using the Caroline D12C System

by Kanat Tolubayev, Bakhyt Zhautikov, Nikolay Zobnin, Guldana Dairbekova and Saule Kabiyeva

Condens. Matter 2025, 10(1), 19; https://doi.org/10.3390/condmat10010019 - 20 Mar 2025

Abstract

In this study, the effects of specific power (1–100 W/cm²), operating pressure (0.5–3.0 Pa), and voltage frequency (20–500 kHz) on film growth kinetics, morphology, and silicon entrainment were investigated to optimize magnetron sputtering for producing thin silicon films suitable for lithium-ion [...] Read more.

In this study, the effects of specific power (1–100 W/cm²), operating pressure (0.5–3.0 Pa), and voltage frequency (20–500 kHz) on film growth kinetics, morphology, and silicon entrainment were investigated to optimize magnetron sputtering for producing thin silicon films suitable for lithium-ion battery anodes. Silicon films were deposited on copper substrates using the Caroline D12C system. The film thickness and morphology were determined using scanning electron microscopy and atomic force microscopy. It was found that the porosity of the films increases with increasing pressure in the working chamber. It was found that the film morphology is non-uniform up to a thickness of 100–150 nm. After that, the film thickness becomes uniform over the entire substrate surface, and the deposition rate increases sharply, i.e., an induction period is observed. The induction period duration decreases with increasing voltage power and frequency. At the same time, silicon removal increases. Frequency has a greater effect on both parameters. The paper specifies a strategy for the technical and economic optimization of the magnetron sputtering process, which determines a compromise between the positive effect of increasing productivity and the negative effect of silicon removal. Full article

► Show Figures

Figure 1

11 pages, 415 KiB

Open AccessArticle

Orbital-Nematic and Two-Fluid Superconductivity in Hole-Doped NdNiO₂

by Luis Craco

Condens. Matter 2025, 10(1), 18; https://doi.org/10.3390/condmat10010018 - 14 Mar 2025

Abstract

Based on DFT + DMFT, we investigate the orbital-nematic and s-wave superconducting states of a hole-doped

{NdNiO}_{2}

superconductor. We emphasize the role played by the interorbital proximity effect in determining the orbital-selective electronic state both in the normal and superconducting phases. [...] Read more.

Based on DFT + DMFT, we investigate the orbital-nematic and s-wave superconducting states of a hole-doped

{NdNiO}_{2}

superconductor. We emphasize the role played by the interorbital proximity effect in determining the orbital-selective electronic state both in the normal and superconducting phases. Specifically, we show how orbital-nematic plus s-wave pairing symmetry acting on the

x z

orbital might have pronounced effects on proximitized non-superconducting Ni-

3 d

orbitals due to many-particle electron–electron interactions. This work represents a step forward in understanding the emergence of two-fluid superconductivity (with superconducting

x z

and non-superconducting

x y, y z, x^{2} - y^{2}, 3 z^{2} - r^{2}

channels) in hole-doped

{NdNiO}_{2}

superconductors. Full article

(This article belongs to the Special Issue Complexity in Quantum Materials: In Honor of Prof. K.A. Muller)

► Show Figures

Figure 1

9 pages, 1767 KiB

Open AccessArticle

Possible Superconductivity in Very Thin Magnesium Films

by Giovanni Alberto Ummarino and Alessio Zaccone

Condens. Matter 2025, 10(1), 17; https://doi.org/10.3390/condmat10010017 - 10 Mar 2025

Cited by 1

Abstract

It is known that noble metals such as gold, silver and copper are not superconductors; this is also true for magnesium. This is due to the weakness of the electron–phonon interaction, which makes them excellent conductors but not superconductors. As has recently been [...] Read more.

It is known that noble metals such as gold, silver and copper are not superconductors; this is also true for magnesium. This is due to the weakness of the electron–phonon interaction, which makes them excellent conductors but not superconductors. As has recently been shown for gold, silver and copper, and even for magnesium, it is possible that in very particular situations, superconductivity may occur. Quantum confinement in thin films has been consistently shown to induce a significant enhancement of the superconducting critical temperature in several superconductors. It is therefore an important fundamental question whether ultra-thin film confinement may induce observable superconductivity in non-superconducting metals such as magnesium. We study this problem using a generalization, in the Eliashberg framework, of a BCS theory of superconductivity in good metals under thin-film confinement. By numerically solving these new Eliashberg-type equations, we find the dependence of the superconducting critical temperature on the film thickness, L. This parameter-free theory predicts superconductivity in very thin magnesium films. We demonstrate that this is a fine-tuning problem where the thickness must assume a very precise value, close to half a nanometer. Full article

(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)

► Show Figures

Figure 1

4 pages, 167 KiB

Open AccessEditorial

High-Precision X-Ray Measurements 2023

by Fabrizio Napolitano and Alessandro Scordo

Condens. Matter 2025, 10(1), 16; https://doi.org/10.3390/condmat10010016 - 6 Mar 2025

Abstract

High-Precision X-ray Measurements 2023 is a Special Issue of the journal Condensed Matter enclosing the scientific content of the 2023 High-Precision X-ray Measurements (HPXRM) conference [...] Full article

(This article belongs to the Special Issue High Precision X-ray Measurements 2023)

18 pages, 1106 KiB

Open AccessArticle

Edelstein Effect in Isotropic and Anisotropic Rashba Models

by Irene Gaiardoni, Mattia Trama, Alfonso Maiellaro, Claudio Guarcello, Francesco Romeo and Roberta Citro

Condens. Matter 2025, 10(1), 15; https://doi.org/10.3390/condmat10010015 - 4 Mar 2025

Abstract

We investigate spin-to-charge conversion via the Edelstein effect in a 2D Rashba electron gas using the semiclassical Boltzmann approach. We analyze the magnetization arising from the direct Edelstein effect, taking into account an anisotropic Rashba model. We study how this effect depends on [...] Read more.

We investigate spin-to-charge conversion via the Edelstein effect in a 2D Rashba electron gas using the semiclassical Boltzmann approach. We analyze the magnetization arising from the direct Edelstein effect, taking into account an anisotropic Rashba model. We study how this effect depends on the effective masses and Rashba spin–orbit coupling parameters, extracting analytical expressions for the high electronic density regime. Indeed, it is possible to manipulate the anisotropy introduced into the system through these parameters to achieve a boost in the Edelstein response compared to the isotropic Rashba model. We also discuss the theoretical framework to study the inverse Edelstein effect and calculate self-consistently the electric current induced by the proximity of the system to a ferromagnet. These results provide insights into the role of Rashba spin–orbit coupling and anisotropic effects in spin–charge conversion phenomena. Full article

(This article belongs to the Special Issue Fluctuations and Highly Non-linear Phenomena in Superfluids and Superconductors VIII)

► Show Figures

Figure 1

11 pages, 480 KiB

Open AccessArticle

Electron Density and Compressibility in the Kitaev Model with a Spatially Modulated Phase in the Superconducting Pairing

by Fabián G. Medina Cuy and Fabrizio Dolcini

Condens. Matter 2025, 10(1), 14; https://doi.org/10.3390/condmat10010014 - 28 Feb 2025

Abstract

A current flowing through a one-dimensional Kitaev chain induces a spatial modulation in its superconducting pairing, characterized by a wavevector Q, which is known to induce two types of topological phase transitions: one is the customary band topology transition between gapped phases, [...] Read more.

A current flowing through a one-dimensional Kitaev chain induces a spatial modulation in its superconducting pairing, characterized by a wavevector Q, which is known to induce two types of topological phase transitions: one is the customary band topology transition between gapped phases, while the other is a Lifshitz transition related to the Fermi surface topology and leading to a gapless superconducting phase. We investigate the behavior of the electron density

ρ

and the compressibility

κ

across the two types of transitions, as a function of the model parameters. We find that the behavior of

ρ

as a function of Q and chemical potential

μ

enables one to infer the ground state phase diagram. Moreover, the analysis of the compressibility

κ

as a function of

μ

enables one to distinguish the two transitions: While

κ

exhibits a symmetric divergence across the band topology transition, it displays an asymmetric jump across the Lifshitz transition. Full article

(This article belongs to the Special Issue Fluctuations and Highly Non-linear Phenomena in Superfluids and Superconductors VIII)

► Show Figures

Figure 1

16 pages, 2650 KiB

Open AccessReview

On a Crystal Chemical Vision on Niobium-Based Superconducting Intermetallics: A Brief Overview

by Taimo Priinits, Artjom Vargunin and Aleksandr Liivand

Condens. Matter 2025, 10(1), 13; https://doi.org/10.3390/condmat10010013 - 14 Feb 2025

Abstract

The present report focuses on the close interplay between condensed matter physics and solid-state chemistry in Nb-based binary intermetallic compounds. Over the recent four decades, these materials have been widely used in the development of a number of superconducting applications and various superconducting [...] Read more.

The present report focuses on the close interplay between condensed matter physics and solid-state chemistry in Nb-based binary intermetallic compounds. Over the recent four decades, these materials have been widely used in the development of a number of superconducting applications and various superconducting devices, including non-standard engineering solutions in the design of large magnets. However, since the 1980s, when it became apparent that the mechanical and superior superconducting properties of ordered intermetallic alloys such as Nb₃Sn were largely due to their unique structural features, much of the research interest in the science of superconducting intermetallic alloys has been redirected to the development of necessary engineering applications in high magnetic field technology. Accordingly, the important role of crystal chemistry in understanding the fundamental aspects of the material properties of the Nb₃Sn family of intermetallics has not been extensively explored. In this paper, we try to fill this gap by investigating the relationships between composition, microstructure and properties, highlighting their relevance to technological applications. Our goal is to combine aspects of crystal chemistry with physical and material application issues. We shed light on the atomic assembly mechanisms and processes in terms of changes in the chemical environment, lattice structure, crystallization pathway, and macroscale phase textures, which can help in interpreting and explaining the prospects and limitations of the superconducting properties of Nb₃Sn. In the context of past and present prospects and limitations, we briefly overview most important technological applications and discuss the various inter-relations between superconductivity and structural properties of Nb-based A-15 intermetallic alloys. We argue that these inter-relations can be used to find Nb-based superconductors with more superior properties and stronger technological usability. Full article

(This article belongs to the Section Superconductivity)

► Show Figures

Figure 1

13 pages, 17818 KiB

Open AccessArticle

Optical Mapping and On-Demand Selection of Local Hysteresis Properties in VO₂

by Melissa Alzate Banguero, Sayan Basak, Nicolas Raymond, Forrest Simmons, Pavel Salev, Ivan K. Schuller, Lionel Aigouy, Erica W. Carlson and Alexandre Zimmers

Condens. Matter 2025, 10(1), 12; https://doi.org/10.3390/condmat10010012 - 13 Feb 2025

Abstract

Quantum materials have tremendous potential for disruptive applications. However, scaling devices down has been challenging due to electronic inhomogeneities in many of these materials. Understanding and controlling these electronic patterns on a local scale has thus become crucial to further new applications. To [...] Read more.

Quantum materials have tremendous potential for disruptive applications. However, scaling devices down has been challenging due to electronic inhomogeneities in many of these materials. Understanding and controlling these electronic patterns on a local scale has thus become crucial to further new applications. To address this issue, we have developed a new optical microscopy method that allows for the precise quasi-continuous filming of the insulator-to-metal transition in VO

_{2}

with fine temperature steps. This enables us to track metal and insulator domains over thousands of images and quantify, for the first time, the local hysteresis properties of VO

_{2}

thin films. The analysis of the maps has allowed us to quantify cycle-to-cycle reproducibility of the local transitions and reveals a positive correlation between the local insulator–metal transition temperatures T

_{c}

and the local hysteresis widths

Δ T_{c}

. These maps also enable the optical selection of regions of high or low transition temperature in combination with large or nearly absent local hysteresis. These maps pave the way to understand and use stochasticity to advantage in these materials by picking on-demand transition properties, allowing the scaling down of devices such as optical switches, infrared microbolometers and spiking neural networks. Full article

(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)

► Show Figures

Figure 1

18 pages, 1287 KiB

Open AccessArticle

Inhomogeneous Evolution of a Dense Ensemble of Optically Pumped Excitons to a Charge Transfer State

by Natasha Kirova and Serguei Brazovskii

Condens. Matter 2025, 10(1), 11; https://doi.org/10.3390/condmat10010011 - 9 Feb 2025

Abstract

Phase transformations induced by short optical pulses are mainstream in studies on the dynamics of cooperative electronic states. We present a semiphenomenological modeling of spatiotemporal effects expected when optical excitons are intricate with the order parameter such as in, e.g., organic compounds with [...] Read more.

Phase transformations induced by short optical pulses are mainstream in studies on the dynamics of cooperative electronic states. We present a semiphenomenological modeling of spatiotemporal effects expected when optical excitons are intricate with the order parameter such as in, e.g., organic compounds with neutral-ionic ferroelectric phase transitions. A conceptual complication appears here, where both the excitation and the ground state ordering are built from the intermolecular electronic transfer. To describe both thermodynamic and dynamic effects on the same root, we adopt, for the phase transition, a view of the excitonic insulator—a hypothetical phase of a semiconductor that appears if the exciton energy becomes negative. After the initial pumping pulse, a quasi-condensate of excitons can appear as a macroscopic quantum state that then evolves, while interacting with other degrees of freedom which are prone to an instability. The self-trapping of excitons enhances their density, which can locally surpass a critical value to trigger the phase transformation. The system is stratified in domains that evolve through dynamical phase transitions and may persist even after the initiating excitons have recombined. Full article

(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)

► Show Figures

Figure 1

Journal Description

Condensed Matter

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Further Information

Guidelines

MDPI Initiatives

Follow MDPI