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Modelling T_c Changes in Strained Sr₂RuO₄

Journal Description

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 19.9 days after submission; acceptance to publication is undertaken in 3.8 days (median values for papers published in this journal in the second half of 2024).
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: 1.9 (2023); 5-Year Impact Factor: 1.5 (2023)

Imprint Information Journal Flyer Open Access ISSN: 2410-3896

Latest Articles

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

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)

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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

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

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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

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)

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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

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)

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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

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

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)

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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

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)

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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

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)

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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

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)

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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

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)

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19 pages, 386 KiB

Open AccessArticle

Strained Graphene as Pristine Graphene with a Deformed Momentum Operator

by David Valenzuela, Alfredo Raya and Juan D. García-Muñoz

Condens. Matter 2025, 10(1), 10; https://doi.org/10.3390/condmat10010010 - 7 Feb 2025

We explore the equivalence between the low-energy dynamics of strained graphene and a quantum mechanical framework for the 2D Dirac equation in flat space with a deformed momentum operator. By considering some common forms of the anisotropic Fermi velocity tensor emerging from the [...] Read more.

We explore the equivalence between the low-energy dynamics of strained graphene and a quantum mechanical framework for the 2D Dirac equation in flat space with a deformed momentum operator. By considering some common forms of the anisotropic Fermi velocity tensor emerging from the elasticity theory, we associate such tensor forms with a deformation of the momentum operator. We first explore the bound states of charge carriers in a background uniform magnetic field in this framework and quantify the impact of strain in the energy spectrum. Then, we use a quadrature algebra formula as a mathematical tool to analyze the impact of the deformation attached to the momentum operator and identify physical consequences of such deformation in terms of energy modifications due to the applied strain. Full article

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10 pages, 349 KiB

Open AccessFeature PaperArticle

Temperature Dependence of the Dynamical and DC Conductivity in 2D Dirac Systems: Self-Consistent Random-Phase-Approximation Approach

by Ivan Kupčić and Patrik Papac

Condens. Matter 2025, 10(1), 9; https://doi.org/10.3390/condmat10010009 - 1 Feb 2025

We studied relaxation processes in heavily doped two-dimensional Dirac systems associated with electron scattering by acoustic and optical phonons and by static disorder. The frequency dependence of the real and imaginary parts of the relaxation function is calculated for different temperatures. The two-component [...] Read more.

We studied relaxation processes in heavily doped two-dimensional Dirac systems associated with electron scattering by acoustic and optical phonons and by static disorder. The frequency dependence of the real and imaginary parts of the relaxation function is calculated for different temperatures. The two-component low-frequency dynamical conductivity is found to be strongly dependent on temperature. At low temperatures, the imaginary part of the zero-frequency relaxation function and the DC resistivity are characterized by the scaling law

a T^{x}

with the exponent x between 2.5 and 3. Full article

(This article belongs to the Special Issue Selected Papers from the International Conference on Quantum Materials and Technologies (ICQMT2024))

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11 pages, 5696 KiB

Open AccessArticle

Structure and Properties of (Fe₈₀Ga₂₀)_99.8Ce_0.2 Alloy in Cast and Hot Rolled State

by Vasily Milyutin, Irina Gervasyeva, Azambek Kalonov, Denis Shishkin, Denis Davydov and Liudmila Stashkova

Condens. Matter 2025, 10(1), 8; https://doi.org/10.3390/condmat10010008 - 30 Jan 2025

FeGa alloys with small additions of rare-earth elements surpass binary alloys in magnetostriction and plasticity. For this reason, they are considered promising magnetostrictive materials for various electrical engineering applications. The alloy (Fe₈₁Ga₁₉)_99.8Ce_0.2 was prepared and investigated [...] Read more.

FeGa alloys with small additions of rare-earth elements surpass binary alloys in magnetostriction and plasticity. For this reason, they are considered promising magnetostrictive materials for various electrical engineering applications. The alloy (Fe₈₁Ga₁₉)_99.8Ce_0.2 was prepared and investigated in this work. It was found that in the cast state, it has a magnetostriction of 3/2 λ about 100 ppm, saturation magnetization of 150 emu/g, tensile strength of about 300 MPa, and fracture strain of 3%. The microstructure, crystallographic texture, and behavior when heated of the alloy were investigated. Then the ingot was subjected to forging and hot rolling with a deformation degree of 90% at 1000 °C. The structure and mechanical properties of samples cut from a hot rolling sheet were studied. Their tensile strength and fracture strain increase compared to cast state up to 600 MPa and 4% correspondingly. Full article

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11 pages, 826 KiB

Open AccessArticle

Density Collective Modes of Exciton Superfluidity in Bilayer Systems

by Filippo Pascucci, Sara Conti, David Neilson, Andrea Perali and Jacques Tempere

Condens. Matter 2025, 10(1), 7; https://doi.org/10.3390/condmat10010007 - 16 Jan 2025

We propose a new way to establish the existence of a superfluid phase in an exciton bilayer system by exploiting the properties of its collective modes. We focus on the density collective modes and treat them within Random Phase Approximation. By comparing results [...] Read more.

We propose a new way to establish the existence of a superfluid phase in an exciton bilayer system by exploiting the properties of its collective modes. We focus on the density collective modes and treat them within Random Phase Approximation. By comparing results for the normal and superfluid states, we are able to identify unambiguous fingerprints of the exciton superfluid phase. We compare the collective modes of the exciton system and cold atom systems, and we discuss the collective modes of the exciton superfluid order parameter. Full article

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

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11 pages, 4413 KiB

Open AccessArticle

Crystal Structure Evolution of Piezoelectric Fe-Doped ZnO Film by Magnetron Co-Sputtering Technique

by Ya-Chih Cheng, Sanjaya Brahma, Sean Wu, Jow-Lay Huang and Alex C. H. Lee

Condens. Matter 2025, 10(1), 6; https://doi.org/10.3390/condmat10010006 - 15 Jan 2025

Zinc oxide (ZnO) exhibits piezoelectric properties due to its asymmetric structure, making it suitable for piezoelectric devices. This experiment deposited Fe-doped ZnO films on silicon substrates using a dual-target magnetron co-sputtering system. The films achieved a high c-axis orientation, and the piezoelectric coefficient [...] Read more.

Zinc oxide (ZnO) exhibits piezoelectric properties due to its asymmetric structure, making it suitable for piezoelectric devices. This experiment deposited Fe-doped ZnO films on silicon substrates using a dual-target magnetron co-sputtering system. The films achieved a high c-axis orientation, and the piezoelectric coefficient of the film reached its optimal value of 44.35 pC/N when doped with 0.5 at% of Fe. This value is approximately three times that of undoped ZnO films with a piezoelectric coefficient of 13.04 pC/N. The study utilized a diffractometer, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy to evaluate the crystal structure evolution of the zinc oxide films and employed X-ray photoelectron spectroscopy to assess the valence state of the Fe ions. Full article

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20 pages, 12787 KiB

Open AccessArticle

Exploring the Properties of Quantum Scars in a Toy Model

by Sudip Sinha and Subhasis Sinha

Condens. Matter 2025, 10(1), 5; https://doi.org/10.3390/condmat10010005 - 12 Jan 2025

We introduce the concept of ergodicity and explore its deviation caused by quantum scars in an isolated quantum system, employing a pedagogical approach based on a toy model. Quantum scars, originally identified as traces of classically unstable orbits in certain wavefunctions of chaotic [...] Read more.

We introduce the concept of ergodicity and explore its deviation caused by quantum scars in an isolated quantum system, employing a pedagogical approach based on a toy model. Quantum scars, originally identified as traces of classically unstable orbits in certain wavefunctions of chaotic systems, have recently regained interest for their role in non-ergodic dynamics, as they retain memory of their initial states. We elucidate these features of quantum scars within the same framework of this toy model. The integrable part of the model consists of two large spins, with a classical counterpart, which we combine with a random matrix to induce ergodic behavior. Scarred states can be selectively generated from the integrable spin Hamiltonian by protecting them from the ergodic states using a projector method. Deformed projectors mimic the ‘quantum leakage’ of scarred states, enabling tunable mixing with ergodic states and thereby controlling the degree of scarring. In this simple model, we investigate various properties of quantum scarring and shed light on different aspects of many-body quantum scars observed in more complex quantum systems. Notably, the underlying classicality can be revealed through the entanglement spectrum and the dynamics of ‘out-of-time-ordered correlators’. Full article

(This article belongs to the Special Issue Non-equilibrium Dynamics in Ultra-Cold Quantum Gases)

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16 pages, 326 KiB

Open AccessArticle

Quantum Kinetic Theory of the Spin Hall Effect for Disordered Graphene with Rashba Spin–Orbit Coupling

by Roberto Raimondi and Thierry Valet

Condens. Matter 2025, 10(1), 4; https://doi.org/10.3390/condmat10010004 - 6 Jan 2025

The spin Hall effect for the model Hamiltonian of graphene with Rashba spin–orbit coupling is analyzed by means of a recently derived quantum kinetic theory of the linear response for multi-band electron systems. The latter expresses the interband part of the density matrix [...] Read more.

The spin Hall effect for the model Hamiltonian of graphene with Rashba spin–orbit coupling is analyzed by means of a recently derived quantum kinetic theory of the linear response for multi-band electron systems. The latter expresses the interband part of the density matrix in terms of the intraband occupation numbers, which can be obtained as solutions of a Boltzmann transport equation. The analysis, which, in the case of the model here considered, can be carried out in a completely analytical way, thus provides an effective pedagogical illustration of the general theory. While our results agree with those previously obtained with alternative approaches for the same model, our comparatively simpler and more physically transparent derivation illustrates the advantages of our formalism when dealing with non trivial multi-band Hamiltonians. Full article

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

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23 pages, 6551 KiB

Open AccessFeature PaperArticle

Anomalous Polarization in One-Dimensional Aperiodic Insulators

by Anouar Moustaj, Julius Krebbekx and Cristiane Morais Smith

Condens. Matter 2025, 10(1), 3; https://doi.org/10.3390/condmat10010003 - 6 Jan 2025

Cited by 1

Multilevel charge pumping is a feature that was recently observed in quasiperiodic systems. In this work, we show that it is more generic and appears in different aperiodic systems. Additionally, we show that for aperiodic systems admitting arbitrarily long palindromic factors, the charge [...] Read more.

Multilevel charge pumping is a feature that was recently observed in quasiperiodic systems. In this work, we show that it is more generic and appears in different aperiodic systems. Additionally, we show that for aperiodic systems admitting arbitrarily long palindromic factors, the charge pumping protocol connects two topologically distinct insulating phases. This confirms the existence of topological phases in aperiodic systems whenever their finite-size realizations admit inversion symmetry. These phases are characterized by an anomalous edge response resulting from the bulk–boundary correspondence. We show that these signatures are all present in various chains, each representing a different class of structural aperiodicity: the Fibonacci quasicrystal, the Tribonacci quasicrystal, and the Thue–Morse chain. More specifically, we calculate three quantities: the Berry phase of the periodic approximation of the finite-size systems, the polarization response to an infinitesimal static and constant electric field in systems with open boundary conditions, and the degeneracy of the entanglement spectrum. We find that all of them provide signatures of a topologically nontrivial phase. Full article

(This article belongs to the Section Condensed Matter Theory)

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8 pages, 4625 KiB

Open AccessArticle

Topological Superconductivity of the Unconventional Type, S = 1, S^z = 0, in a Layer of Adatoms

by Edine Silva and Mucio A. Continentino

Condens. Matter 2025, 10(1), 2; https://doi.org/10.3390/condmat10010002 - 5 Jan 2025

In this paper, we study the appearance of topological p-wave superconductivity of the type

S = 1

,

S^{z} = 0

in a layer of adatoms. This unconventional superconductivity arises due to an anti-symmetric hybridization between the orbitals of the adatoms [...] Read more.

In this paper, we study the appearance of topological p-wave superconductivity of the type

S = 1

,

S^{z} = 0

in a layer of adatoms. This unconventional superconductivity arises due to an anti-symmetric hybridization between the orbitals of the adatoms and those of the atoms in the superconducting BCS substrate. This two-dimensional system is topologically non-trivial only in the absence of a magnetic field and belongs to class DIII of the Altland–Zirnbauer classification. We obtain the Pfaffian that characterizes the topological phases of the system and its phase diagram. We discuss the differences between the two-dimensional case and a chain with the same type of superconductivity. Full article

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

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11 pages, 4730 KiB

Open AccessArticle

Terahertz Time-Domain Spectroscopy of Substituted Gadolinium Gallium Garnet

by Ke Wang, Junchao Xu, Hironaru Murakami, Hiroyasu Yamahara, Munetoshi Seki, Hitoshi Tabata and Masayoshi Tonouchi

Condens. Matter 2025, 10(1), 1; https://doi.org/10.3390/condmat10010001 - 25 Dec 2024

Temperature dependence of the lowest frequency transverse optical phonon (TO1) in a single crystal Substituted Gadolinium Gallium Garnet (SGGG, (001)) was studied using terahertz time-domain spectroscopy at temperatures between 80 K and 500 K. The complex dielectric constants were calculated from the optical [...] Read more.

Temperature dependence of the lowest frequency transverse optical phonon (TO1) in a single crystal Substituted Gadolinium Gallium Garnet (SGGG, (001)) was studied using terahertz time-domain spectroscopy at temperatures between 80 K and 500 K. The complex dielectric constants were calculated from the optical constants fitting with the Lorentz oscillator model. The results show that the TO1 phonon of SGGG is at 2.5 THz at room temperature, the frequency of the TO1 phonon slightly decreases, and the dumping factor clearly increases with increasing temperature. Additionally, our results demonstrate that even a small substitution can induce a phonon shift, leading to higher absorption and causing a slight degradation in thermal stability. Our work is expected to support the development of magneto-optical and spintronic devices. Full article

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Selected Papers from the Annual Global Summit on Nanotechnology and Materials Science (AGSNANOMAT2025) Guest Editors: Vladimir Sobolev, Binhao Wang
Deadline: 15 October 2025

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