Superstripes Physics, 3rd Edition

A special issue of Condensed Matter (ISSN 2410-3896). This special issue belongs to the section "Quantum Materials".

Deadline for manuscript submissions: closed (30 April 2025) | Viewed by 15453

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Rome International Center for Materials Science Superstripes (RICMASS), Via dei Sabelli 119A, 00185 Roma, Italy
Interests: synchrotron radiation research; protein fluctuations; active sites of metalloproteins; origin of life; selected molecules in prebiotic world; quantum phenomena in complex matter; quantum confinement; superstripes in complex matter; lattice complexity in transition metal oxides; high Tc superconductors; valence fluctuation materials
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Department of Physics, Columbia University, New York, NY 10027, USA
Interests: atomic, molecular, and optical physics; condensed matter physics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue will publish selected papers from the Superstripes 2024 meeting due to take place June 24–29, 2024, in Ischia–Naples, Italy.

The Superstripes 2024 meeting continues a successful series of international meetings, which first began in Rome in 1996 following growing scientific interest in the emergence new phenomena related to complexity in quantum matter. The aim of the Superstripes 2024 meeting is to foster advances in top-level science and scientific culture, bringing together selected world leaders in the field of quantum complex matter science. You are invited to contribute an article or review paper for possible publication in our Special Issue. Submissions will be rapidly reviewed and published shortly, if accepted.

Prof. Dr. Antonio Bianconi
Prof. Dr. Yasutomo Uemura
Guest Editors

Manuscript Submission Information

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Keywords

  • quantum complex matter
  • symmetry and heterogeneity
  • multi-condensates
  • topological materials
  • superstripes
  • stripes

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Published Papers (14 papers)

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Research

Jump to: Review

9 pages, 1767 KiB  
Article
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
Viewed by 1818
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)
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13 pages, 17818 KiB  
Article
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
Viewed by 894
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 VO­2 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 VO­2 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 T­c and the local hysteresis widths ΔTc. 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  
Article
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
Viewed by 633
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)
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8 pages, 4625 KiB  
Article
Topological Superconductivity of the Unconventional Type, S = 1, Sz = 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
Viewed by 870
Abstract
In this paper, we study the appearance of topological p-wave superconductivity of the type S=1, Sz=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, Sz=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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14 pages, 1835 KiB  
Article
Magnetic and Electronic Inhomogeneity in Sm1−xEuxB6
by M. Victoria Ale Crivillero, Priscila F. S. Rosa, Zachary Fisk, Jens Müller, Pedro Schlottmann and Steffen Wirth
Condens. Matter 2024, 9(4), 55; https://doi.org/10.3390/condmat9040055 - 13 Dec 2024
Cited by 1 | Viewed by 887
Abstract
While SmB6 attracts attention as a possible topological Kondo insulator, EuB6 is known to host magnetic polarons that give rise to large magnetoresistive effects above its ferromagnetic order transition. Here, we investigate single crystals of Sm1−xEuxB6 [...] Read more.
While SmB6 attracts attention as a possible topological Kondo insulator, EuB6 is known to host magnetic polarons that give rise to large magnetoresistive effects above its ferromagnetic order transition. Here, we investigate single crystals of Sm1−xEuxB6 by magnetic and magnetotransport measurements to explore a possible interplay of these two intriguing phenomena, with a focus on the Eu-rich substitutions. Sm0.01Eu0.99B6 exhibits generally similar behavior as EuB6. Interestingly, Sm0.05Eu0.95B6 combines a global antiferromagnetic order with local polaron formation. A pronounced hysteresis is found in the magnetoresistance of Sm0.1Eu0.9B6 at low temperature (T= 1.9 K) and applied magnetic fields between 2.3 and 3.6 T. The latter is in agreement with a phenomenological model that predicts the stabilization of ferromagnetic polarons with an increasing magnetic field within materials with a global antiferromagnetic order. Full article
(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)
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11 pages, 1091 KiB  
Article
The Effect of an Anisotropic Scattering Rate on the Magnetoresistance of a Metal: A Cuprate-Inspired Analysis
by Giovanni Mirarchi and Sergio Caprara
Condens. Matter 2024, 9(4), 52; https://doi.org/10.3390/condmat9040052 - 29 Nov 2024
Viewed by 790
Abstract
Inspired by the phenomenology of high-critical-temperature superconducting cuprates, we investigate the effect of an anisotropic scattering rate on the magnetoresistance of a metal, relying on Chambers’ solution to the Boltzmann equation. We find that if the scattering rate is enhanced near points of [...] Read more.
Inspired by the phenomenology of high-critical-temperature superconducting cuprates, we investigate the effect of an anisotropic scattering rate on the magnetoresistance of a metal, relying on Chambers’ solution to the Boltzmann equation. We find that if the scattering rate is enhanced near points of the Fermi surface with a locally higher density of states, an extended regime is found where the magnetoresistance varies linearly with the magnetic field. We then apply our results to fit the experimental magnetoresistance of La1.6−xNd0.4SrxCuO4 and speculate about the possible source of anisotropic scattering. Full article
(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)
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16 pages, 509 KiB  
Article
Single-Defect-Induced Peculiarities in Inverse Faraday-Based Switching of Superconducting Current-Carrying States near a Critical Temperature
by Mihail D. Croitoru and Alexander I. Buzdin
Condens. Matter 2024, 9(4), 48; https://doi.org/10.3390/condmat9040048 - 12 Nov 2024
Viewed by 934
Abstract
The Inverse Faraday Effect (IFE) is a phenomenon that enables non-thermal magnetization in various types of materials through the interaction with circularly polarized light. This study investigates the impact of single defects on the ability of circularly polarized radiation to switch between distinct [...] Read more.
The Inverse Faraday Effect (IFE) is a phenomenon that enables non-thermal magnetization in various types of materials through the interaction with circularly polarized light. This study investigates the impact of single defects on the ability of circularly polarized radiation to switch between distinct superconducting current states, when the magnetic flux through a superconducting ring equals half the quantum flux, Φ0/2. Using both analytical methods within the standard Ginzburg–Landau theory and numerical simulations based on the stochastic time-dependent Ginzburg–Landau approach, we demonstrate that while circularly polarized light can effectively switch between current-carrying superconducting states, the presence of a single defect significantly affects this switching mechanism. We establish critical temperature conditions above which the switching effect completely disappears, offering insights into the limitations imposed by a single defect on the dynamics of light-induced IFE-based magnetization in superconductors. Full article
(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)
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13 pages, 1122 KiB  
Article
Simple Model for Tc and Pairing Symmetry Changes in Sr2RuO4 Under (100) Uniaxial Strain
by Macauley Curtis, Martin Gradhand and James F. Annett
Condens. Matter 2024, 9(4), 44; https://doi.org/10.3390/condmat9040044 - 1 Nov 2024
Viewed by 1154
Abstract
Uniaxial strain in the (100) direction has the effect of increasing the superconducting Tc in Sr2RuO4 from 1.5 K to over 3 K. The enhanced Tc corresponds to a Lifshitz transition in the Fermi surface topology of this [...] Read more.
Uniaxial strain in the (100) direction has the effect of increasing the superconducting Tc in Sr2RuO4 from 1.5 K to over 3 K. The enhanced Tc corresponds to a Lifshitz transition in the Fermi surface topology of this unconventional superconductor. We model this using a simple two-dimensional one-band model for the γ sheet of the Fermi surface. This reproduces the experimental Tc results well if we assume a dx2y2 singlet pairing state. On the other hand, the triplet state px+ipy does not show any distinct peaks in Tc associated with the Lifshitz transition. A mixed symmetry state pairing of the form d+ig can both describe the Tc changes and show a distinct transition temperature for time-reversal symmetry breaking (TRSB). Full article
(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)
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10 pages, 2113 KiB  
Article
Kondo Versus Fano in Superconducting Artificial High-Tc Heterostructures
by Gaetano Campi, Gennady Logvenov, Sergio Caprara, Antonio Valletta and Antonio Bianconi
Condens. Matter 2024, 9(4), 43; https://doi.org/10.3390/condmat9040043 - 31 Oct 2024
Cited by 1 | Viewed by 1210
Abstract
Recently, the quest for high-Tc superconductors has evolved from the trial-and-error methodology to the growth of nanostructured artificial high-Tc superlattices (AHTSs) with tailor-made superconducting functional properties by quantum design. Here, we report the growth by molecular beam epitaxy (MBE) of a superlattice of [...] Read more.
Recently, the quest for high-Tc superconductors has evolved from the trial-and-error methodology to the growth of nanostructured artificial high-Tc superlattices (AHTSs) with tailor-made superconducting functional properties by quantum design. Here, we report the growth by molecular beam epitaxy (MBE) of a superlattice of Mott insulator metal interfaces (MIMIs) made of nanoscale superconducting layers of quantum confined-space charge in the Mott insulator La2CuO4 (LCO), with thickness L intercalated by normal metal La1.55Sr0.45CuO4 (LSCO) with period d. The critical temperature shows the superconducting dome with Tc as a function of the geometrical parameter L/d showing the maximum at the magic ratio L/d = 2/3 where the Fano–Feshbach resonance enhances the superconducting critical temperature. The normal state transport data of the samples at the top of the superconducting dome exhibit Planckian T-linear resistivity. For L/d > 2/3 and L/d < 2/3, the heterostructures show a resistance following Kondo universal scaling predicted by the numerical renormalization group theory for MIMI nanoscale heterostructures. We show that the Kondo temperature, TK, and the Kondo scattering amplitude, R0K, vanish at L/d = 2/3, while TK and R0K increase at both sides of the superconducting dome, indicating that the T-linear resistance regime competes with the Kondo proximity effect in the normal phase of MIMIs. Full article
(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)
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12 pages, 846 KiB  
Article
Undamped Higgs Modes in Strongly Interacting Superconductors
by José Lorenzana and Götz Seibold
Condens. Matter 2024, 9(4), 38; https://doi.org/10.3390/condmat9040038 - 30 Sep 2024
Viewed by 1051
Abstract
In superconductors, gauge U(1) symmetry is spontaneously broken. According to Goldstone’s theorem, this breaking of a continuous symmetry establishes the existence of the Bogoliubov phase mode while the gauge-invariant response also includes the amplitude fluctuations of the order parameter. The [...] Read more.
In superconductors, gauge U(1) symmetry is spontaneously broken. According to Goldstone’s theorem, this breaking of a continuous symmetry establishes the existence of the Bogoliubov phase mode while the gauge-invariant response also includes the amplitude fluctuations of the order parameter. The latter, which are also termed ‘Higgs’ modes in analogy with the standard model, appear at the energy of the spectral gap 2Δ, when the superconducting ground state is evaluated within the weak-coupling BCS theory, and, therefore, are damped. Previously, we have shown that, within the time-dependent Gutzwiller approximation (TDGA), Higgs modes appear inside the gap with a finite binding energy relative to the quasiparticle continuum. Here, we show that the binding energy of the Higgs mode becomes exponentially small in the weak-coupling limit converging to the BCS solution. On the other hand, well-defined undamped amplitude modes exist in strongly coupled superconductors when the interaction energy becomes of the order of the bandwidth. Full article
(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)
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9 pages, 1098 KiB  
Article
Room-Temperature Superconductivity in 1D
by Carlo A. Trugenberger
Condens. Matter 2024, 9(3), 34; https://doi.org/10.3390/condmat9030034 - 8 Sep 2024
Cited by 2 | Viewed by 1924
Abstract
We review the theoretical model underpinning the recently reported room-temperature, ambient-pressure superconductivity along line defects on the surface of highly oriented pyrolytic graphite. The main ingredients for this 1D room-temperature superconductivity are pairing by effective strain gauge fields, the formation of an effective [...] Read more.
We review the theoretical model underpinning the recently reported room-temperature, ambient-pressure superconductivity along line defects on the surface of highly oriented pyrolytic graphite. The main ingredients for this 1D room-temperature superconductivity are pairing by effective strain gauge fields, the formation of an effective Josephson junction array in its Bose metal state on the surface and the suppression of phase slips by dimensional embedding in an extremely well-conducting 3D bulk structure. Full article
(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)
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Review

Jump to: Research

14 pages, 991 KiB  
Review
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
Viewed by 295
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)
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15 pages, 1834 KiB  
Review
Multiband Superconductivity, Polarons, Jahn-Teller Polarons, Heterogeneity, and High-Temperature Superconductivity
by Annette Bussmann-Holder and Hugo Keller
Condens. Matter 2024, 9(4), 56; https://doi.org/10.3390/condmat9040056 - 19 Dec 2024
Viewed by 962
Abstract
Early on, oxides were ruled out from superconductivity, since they are typically large-band-gap insulators. Nevertheless, a rather small number of them were found to be superconducting, with transition temperatures up to 14 K and a remarkably low carrier density. This was the starting [...] Read more.
Early on, oxides were ruled out from superconductivity, since they are typically large-band-gap insulators. Nevertheless, a rather small number of them were found to be superconducting, with transition temperatures up to 14 K and a remarkably low carrier density. This was the starting point of K. Alex Müller (KAM) becoming interested in superconductivity in oxides. Step by step, he advanced the research on oxides and finally discovered, together with J. Georg Bednorz, high-temperature superconductivity (HTSC) in the perovskite-type compound Ba-La-Cu-O. Even though he was inspired by specific and clear ideas in his search, he added new impact in the understanding of HTSC for many years after receipt of the Nobel prize for this discovery. Full article
(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)
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10 pages, 546 KiB  
Review
Josephson Critical Currents and Related Effects in Ultracold Atomic Superfluid Sytems
by Verdiana Piselli, Leonardo Pisani and Giancarlo Calvanese Strinati
Condens. Matter 2024, 9(4), 41; https://doi.org/10.3390/condmat9040041 - 30 Oct 2024
Viewed by 1012
Abstract
The Josephson and Proximity effects play a pivotal role in the design of superconducting devices for the implementation of quantum technology, ranging from the standard Al based to the more exotic twisted high-Tc junctions. Josephson critical currents have been recently [...] Read more.
The Josephson and Proximity effects play a pivotal role in the design of superconducting devices for the implementation of quantum technology, ranging from the standard Al based to the more exotic twisted high-Tc junctions. Josephson critical currents have been recently investigated also in ultracold atomic systems where a potential barrier acts as a weak link. The unifying feature of the above systems, apart from being superconducting/superfluid, is the presence of spatial inhomogeneity, a feature that has to be properly taken into account in any theoretical approach employed to investigate them. In this work, we review the novel (dubbed LPDA for Local Phase Density Approximation) approach based on a coarse graining of the Bogoliubov–de Gennes (BdG) equations. Non-local and local forms of this coarse graining were utilized when investigating Proximity and Josephson effects. Moreover, the LPDA approach was further developed to include pairing fluctuations at the level of the non-self-consistent t-matrix approximation. The resulting approach, dubbed mLPDA (modified LPDA), can be used whenever inhomegeneity and fluctuations effects simultaneously play an important role. Full article
(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)
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