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Possible high Tc superconductivity in the Ba-La-Cu-O system
Abstract
Metallic, oxygen-deficient compounds in the Ba–La–Cu–O system, with the composition Ba
x
La5–x
Cu5O5(3–y) have been prepared in polycrystalline form. Samples withx=1 and 0.75,y>0, annealed below 900C under reducing conditions, consist of three phases, one of them a perovskite-like mixed-valent copper compound. Upon cooling, the samples show a linear decrease in resistivity, then an approximately logarithmic increase, interpreted as a beginning of localization. Finally an abrupt decrease by up to three orders of magnitude occurs, reminiscent of the onset of percolative superconductivity. The highest onset temperature is observed in the 30 K range. It is markedly reduced by high current densities. Thus, it results partially from the percolative nature, bute possibly also from 2D superconducting fluctuations of double perovskite layers of one of the phases present.
... At Tc = 9.2 K, Nb required another 17 years to be found as a superconductive element [3,4]. More than 2000 superconducting materials were discovered in 1975, and the superconducting transition temperature had reached 22.3 K with the discovery of A-15 compounds such as, Nb3Ge, in 1973 [6][7][8]. Sleight et al. [9], reported in 1975 that superconductivity was seen in BaPb (1-x) BixO3 and the superconducting transition temperature of this compound changes with the Bi/Pb ratio and reached the highest value of 13 K. ...
... The alloy Nb3Ge possessed the greatest superconducting transition temperature, Tc=23. 2 K, until 1986. Early in 1986, Bednorz and Müller [8] discovered that a mixed-phase lanthanum, barium, and copper oxide in the form of a ceramic became superconducting at Tc = 30 K. At the University of Tokyo, Takagi et al. [10] showed that such superconducting temperature range of Ba-substituted La2CuO4 was just as high as 30 K by c the end of 1986. Lanthanum compound by the beginning of 1987 became superconductor at Tc = 40 K at ambient pressure [8,10,11] as well as up to 52 K at high pressure [11]. ...
... Early in 1986, Bednorz and Müller [8] discovered that a mixed-phase lanthanum, barium, and copper oxide in the form of a ceramic became superconducting at Tc = 30 K. At the University of Tokyo, Takagi et al. [10] showed that such superconducting temperature range of Ba-substituted La2CuO4 was just as high as 30 K by c the end of 1986. Lanthanum compound by the beginning of 1987 became superconductor at Tc = 40 K at ambient pressure [8,10,11] as well as up to 52 K at high pressure [11]. La3Ba3Cu6Oy systems demonstrated a superconducting transition temperature of Tc 80 K [12][13][14][15][16][17]. ...
Large-scale applications of high-temperature superconductors (HTSCs) require superconductors with high critical current density operating at 77 K in a strong magnetic field. However, some challenges are faced in large-scale applications such as strong superconducting anisotropy, their irreversible and critical current density values under high field at 77 K not high enough. In this review, the effect of different carbon nanostructures such as carbon nanotubes (CNTs), graphene, and graphene oxide on HTSCs was discussed. In addition, the effect of some metal and metal oxide nanoparticles on HTSCs was reviewed. It was noted that adding nanoparticles and quantum dots at lower concentrations to HTSCs is one of the most efficient ways to increase their critical current density and flux pinning.
... For this reason, the scientific community has continuously searched for new superconducting materials characterized by higher critical temperatures. The first milestone can be identified with the announcement of superconductivity at 30 K in the layered cuprate LaBa 2 CuO 4−x by Bednorz and Muller [9], followed soon after (at the beginning of 1987) by the report of a T C as high as 92 K for the YBa 2 Cu 3 O x compound [10], thus opening the field to superconducting applications at temperatures above the boiling point of liquid nitrogen (77 K). Several compounds in the family of cuprates (either hole-doped or electron-doped) have been identified with T C up to 130 K in Hg 2 Ba 2 Ca 2 Cu 3 O x . ...
... Further advances are represented by the discovery of new unconventional superconductors such as the chiral spin-triplet Sr 2 RuO 4 [14], the two-band superconductor MgB 2 [15][16][17][18][19][20][21], the iron-pnictide superconductors with the so-called s±,++ pairing symmetry [22], where the hole and electron pockets develop distinct s-wave gaps having an intrinsic phase difference of 0(s++) or π(s±), filled skutterudite [23], and layered BiS 2 -based compounds [24]. layered cuprate LaBa2CuO4−x by Bednorz and Muller [9], followed soon after (at the beginning of 1987) by the report of a TC as high as 92 K for the YBa2Cu3Ox compound [10], thus opening the field to superconducting applications at temperatures above the boiling point of liquid nitrogen (77 K). Several compounds in the family of cuprates (either holedoped or electron-doped) have been identified with TC up to 130 K in Hg2Ba2Ca2Cu3Ox. ...
... In particular, exotic superconductivity seems to prefer a layered crystal structure. For example, high TC superconductivity is observed in layered materials, such as cuprates [9,10,159,160], Fe-based [22,[161][162][163][164][165][166][167], and MgB2 [15,168] materials. Among the layered superconductors, the chalcogenides constitute one of the most interesting groups, due to the observation of exotic superconductivity. ...
The family of BiS2-based superconductors has attracted considerable attention since their discovery in 2012 due to the unique structural and electronic properties of these materials. Several experimental and theoretical studies have been performed to explore the basic properties and the underlying mechanism for superconductivity. In this review, we discuss the current understanding of pairing symmetry in BiS2-based superconductors and particularly the role of point-contact spectroscopy in unravelling the mechanism underlying the superconducting state. We also review experimental results obtained with different techniques including angle-resolved photoemission spectroscopy, scanning tunnelling spectroscopy, specific heat measurements, and nuclear magnetic resonance spectroscopy. The integration of experimental results and theoretical predictions sheds light on the complex interplay between electronic correlations, spin fluctuations, and Fermi surface topology in determining the coupling mechanism. Finally, we highlight recent advances and future directions in the field of BiS2-based superconductors, underlining the potential technological applications.
... Understanding the microscopic physics of large, interacting quantum materials such as unconventional superconductors [1] has been a long-standing challenge in theoretical condensed matter physics. A key step toward this goal are reduced models that capture the essential physics, but are simple enough that they can be simulated on classical or todays quantum computers. ...
... If not stated differently, we additionally enforce a global spin flip symmetry by defining ψ(σ) sym = s(σ) 1 2 (ψ(σ) +ψ(T σ)), where the realvalued determinant ψ(σ) = s(σ)ψ(σ) is split into its sign s(σ) andψ(σ), and T flips all spins of σ. ...
Simulating large, strongly interacting fermionic systems remains a major challenge for existing numerical methods. In this work, we present, for the first time, the application of neural quantum states - specifically, hidden fermion determinant states (HFDS) - to simulate the strongly interacting limit of the Fermi-Hubbard model, namely the model, across the entire doping regime. We demonstrate that HFDS achieve energies competitive with matrix product states (MPS) on lattices as large as sites while using several orders of magnitude fewer parameters, suggesting the potential for efficient application to even larger system sizes. This remarkable efficiency enables us to probe low-energy physics across the full doping range, providing new insights into the competition between kinetic and magnetic interactions and the nature of emergent quasiparticles. Starting from the low-doping regime, where magnetic polarons dominate the low energy physics, we track their evolution with increasing doping through analyses of spin and polaron correlation functions. Our findings demonstrate the potential of determinant-based neural quantum states with inherent fermionic sign structure, opening the way for simulating large-scale fermionic systems at any particle filling.
... The pairing mechanism of high-temperature (high T c ) superconductors (SCs) is one of the most important questions in condensed matter [1][2][3]. Since the discovery of cuprates [1], tremendous efforts have been spent on finding new hightemperature superconductors. As a neighborhood of copper, nickelates have long been proposed as an ideal system for realizing high T c SC [4,5]. ...
... The pairing mechanism of high-temperature (high T c ) superconductors (SCs) is one of the most important questions in condensed matter [1][2][3]. Since the discovery of cuprates [1], tremendous efforts have been spent on finding new hightemperature superconductors. As a neighborhood of copper, nickelates have long been proposed as an ideal system for realizing high T c SC [4,5]. ...
Motivated by recent photoemission measurements on the LaSrNiO, we carry out a systematic study of the infinite-layer nickelate using both dynamical mean-field theory and density matrix embedding theory. The renormalized electronic structure and Fermi surface of correlated LaSrNiO are studied in an effective two-band model through the dynamical mean-field calculation. We find the correlation effects reflect mainly on the Ni d band, which is consistent with the experimental findings. We further study the ground state including magnetism and superconductivity through the density matrix embedding theory. Within the experimental doping range and rigid-band approximation, we show that the d-wave superconductivity is the lowest energy state, while the static magnetism is absent except very close to zero doping. These findings provide a new understanding of infinite-layer nickelate superconductivity.
... Although several significant advancements have been presented, from the initial discovery of a superconductor, the most impressive discoveries are CuO2-based superconductors (i.e., high-Tc cuprates) [2]. This is because, prior to this result, superconductors generally require significantly high refrigeration because of their lower critical temperature (~20 K). ...
... (Recent H-based superconductors [6] with extremely high pressures have high potential to be applied 2 to the BCS theory.) Moreover, many claimed that it is related to many-body interactions [7], which made many theoretical researchers' approaches to the mechanism difficult. ...
This study describes all the properties of high Tc cuprates by introducing rotating holes that are created by angular momentum conservations on a 2D CuO2 surface, and which have a different mass from that of a normal hole because of the magnetic field energy induced by the rotation. This new particle called a macroscopic Boson describes the doping dependences of pseudo-gap temperature and the transition temperature at which an anomaly metal phase appears and describes the origin of the pseudo-gap. Furthermore, this study introduces a new model to handle many-body interactions, which results in a new statistic equation. This statistic equation describing many-body interactions accurately explains why high Tc cuprates have significantly high critical temperatures. Moreover a partition function of macroscopic Bosons describes all the properties of anomaly metal phase, which sufficiently agree with experiments, using the result from our previous study [1] that analytically describes the doping dependence of Tc. By introducing a macroscopic Boson and the new statistical model for many-body interactions, this study uncovered the mystery of high Tc cuprates, which have been a challenge for many researchers. An important point is that, in this study, pure analytical calculations are consistently conducted, which agree with experimental data well (i.e., they do not use numerical calculations or fitting methods but use many actual physical constants).
... Esse formalismo complementa a teoria BCS ao explicar o comportamento dos pares de Cooper [2,15]. No entanto, a teoria BCS apresenta limitações em HTSCS [4],em que os mecanismos de interação não são explicados somente por fônons . Para esses casos, é necessário ajustar a teoria para incluir efeitos como o tunelamento entre camadas [1,13,11,10].Nesse contexto uma abordagem na qual seja reexaminada a questão energética, que intermedeia a interação entre elétrons em planos diferentes em um sistema Quase 2D, é examinada em termos de flutuações de partículas e campos no estado do vácuo.Nesse estado, uma região em que dois planos neutros paralelos,cuja a área (A) é muito maior que a distância (d) entre eles resulta em uma menor densidade de energia na região entre os planos gerando uma força de atração.Este efeito Foi descoberto por Casimir em 1948 e confirmado experimentalmente por Lamoreaux [7,14,8].No contexto dos HTSCs,a energia de Casimir favorece à formação de pares em planos modelados como planos de plasma [6,3,12,9] ...
... During the era between 1950 to the 1970 often referred to as initial surge, significant attention was devoted to exploring the thermoelectric characteristics of numerous straightforward conducting oxides such as CdO, NiO, ZnO, In2O3, SrTiO3, rutile-TiO2, SnO2, Cu2O and Fe3O4 were investigated in 1st Boom for the estimation of physical characteristics of like as effective mass of carriers [14][15][16][17][18][19][20][21][22]. The superconducting oxides (high Tc) like as La2CuO4, La-Ba-Cu-O, YBa2-Cu3O7-δ, and Tl-Ca-Ba-Cu-O, were investigated for thermoelectric properties in 2nd Boom [23][24][25][26][27]. Some other superconducting materials (high Tc) like as CaMnO3, Al doped ZnO and NaxCoO2 with excellent thermoelectric results were also documented by the Ohtaki and Terasaki [28][29][30]. ...
Zinc cobalt oxide nanostructures were synthesized by electrochemical deposition of zinccobalt alloy at various bath temperatures (15, 30, 45 and 60 ˚C) and its hydrothermal oxidation at 100 ˚C. X-ray diffraction pattern and Raman spectroscopy data reveals the formation of spinal structure of ZnCo2O4. Photoluminescence spectra of the samples exhibit broad peaks with a red shift in the emission energy. Diffused reflectance spectroscopy measured the band gap of the synthesized materials; band gap is 3.06, 3.03, 3.02 and 2.99 eV, for samples electrodeposited at 15, 30, 45 and 60 ˚C, respectively. Optical conductivity of synthesized materials decreases with increasing deposition layers while reflectance shows opposite trend. Thermoelectric set up measures the change in potential difference through synthesized materials when different temperatures are applied and an increment in potential were observed. Seebeck co-efficient and power factor are also studied as function of bath temperature.
... The discovery of high-temperature superconductivity in doped cuprates [1] has shaped the field of contemporary condensed matter physics for almost four decades. Tremendous progress has been made in understanding their rich phase diagram, including the exotic normal phases from which superconductivity arises; nonetheless, a unified understanding remains elusive [2,3]. ...
One of the key features of hole-doped cuprates is the presence of an extended pseudogap phase, whose microscopic origin has been the subject of intense investigation since its discovery and is believed to be crucial for understanding high-temperature superconductivity. Various explanations have been proposed for the pseudogap, including links to symmetry-breaking orders such as stripes or pairing, and the emergence of novel fractionalized Fermi liquid (FL*) phases. The topological nature of the FL* phase has been identified as a scenario compatible with a small Fermi surface without symmetry breaking, as suggested experimentally. With recent experimental and numerical studies supporting an intricate relationship between stripe order and the pseudogap phase, we here propose an alternative FL* scenario: a fractionalized Fermi liquid with a geometric origin (GFL*) driven by fluctuating domain walls. The essential mechanism behind our proposal is hidden order, where the proliferation of domain walls stabilized by charge fluctuations obscures the underlying long-range antiferromagnetic order in real-space, but order is preserved in the reference frame of the background spins. As a result, well-defined fermionic quasiparticles in the form of magnetic polarons exist, which couple to topological excitations of the domain wall string-net condensate in the ground state and constitute a small Fermi surface. At a critical doping value, we argue that hidden order is lost, driving a transition to a regular Fermi liquid at a hidden quantum critical point (hQCP) featuring quantum critical transport properties. Our GFL* framework provides a compelling connection between the antiferromagnetic, stripe, and pseudogap phases, and suggests a possible unification of superconductivity in (electron and hole) doped cuprates and heavy fermion compounds.
... In 1987, just one year after the discovery of hightemperature superconductivity (high-T c SC) in cuprates [1], Philip W. Anderson proposed [2] his famous resonating valence bond (RVB) state as the ground state wave-function to describes the properties of such compounds. In essence, the RVB represents a quantum liquid of valence bonds, i.e., a collection of spin sin- ...
Valence bond (VB) states as the formation mechanism of Cooper pairs, eventually leading to high-temperature superconductivity, remain a controversial topic. Although various VB-like states find variational relevance in the description of specific spin models and quantum spin liquids, in the realm of many-body fermionic Hamiltonians, the evidence for such states as ground states wave functions remains elusive, challenging the valence-bond pairing mechanism. Here, we present evidence of a VB ground state with pairing tendencies, particularly at finite doping. We achieved this for the generic two-orbital Hubbard model in low dimension, where the VB states can be associated with the presence of the topological order manifested by edge states. Utilizing density-matrix renormalization group calculations, the study reveals key properties akin to those observed in superconductors' phase diagrams, such as pairing restricted to the regime of small but nonzero doping, presence of coherent pairs, and density oscillations in the charge sector.
... Prior to 1986, all superconductors operated at lower than 35 K and were described as low-temperature superconductors (LTSs). In 1986, superconductivity was discovered in Ba-La-Cu-O 11 and, soon after, in yttrium barium copper oxide (YBCO) at 93 K 12 . This temperature is above the boiling point of nitrogen (77 K). ...
... Since the discovery of high-temperature superconductivity (HTSC) by Bednorz & Müller [1] in 1986, the underlying mechanism has remained an unsolved mystery to this day, although the physics community is certain that the mechanisms crucial for superconductivity take place in the CuO2 levels and the CuO2 layers serve as a charge carrier reservoir. For hole-doped HTSC it is called "hole conduction" ...
... Decades later, the BCS theory explained this magical phenomenon, attributing it to the formation of Cooper pairs through electron-phonon interactions 2 . However, the emergence of high-temperature superconductors (HTS), such as those based on copper [3][4][5] , iron [6][7][8] , and most recently discovered nickel 9 , posed a formidable challenge to established theories. One of the big challenges to understanding these materials is that the conventional model of electron motion in solids no longer holds true 10,11 . ...
Despite decades of research, the origin of high-temperature superconductivity is still unclear, and its microscopic mechanism remains a subject of intense debate. The intrinsic Mott insulating properties of copper oxide parent compounds and the experimentally observed charge-ordered phases in real space suggest that high-temperature superconductivity may stem from localized electrons rather than itinerant electrons. In this work, we propose a unified microscopic mechanism where confined electrons within polyhedral quantum wells represent the Mott ground state, and symmetry-breaking of electron-hole pairs acts as the superconducting mechanism. A single parameter formula for the critical temperature (Tc) of unconventional superconductors is developed, allowing accurate determination of Tc based on lattice constants. The approach elucidates relationships between various charge-order phases and doping concentration, explores Fermi surface structures, investigates spin resonance peaks and parities, and examines pressure-induced dual superconducting phase transitions - all consistent with experimental observations. It is also estimated that the highest Tc of the newly discovered nickel-based superconductor will not exceed 100 K. This work offers critical insights into unconventional superconductivity’s fundamental mechanisms while introducing a new paradigm to reveal more intrinsic connections between superconductivity, conductivity, and magnetism.
... One of the milestones in condensed matter physics is the discovery of high-T c superconductivity in cuprates [1], in which superconductivity with the highest transition temperature of about 135 K was realized [2] at ambient pressure. However, the Bardeen-Cooper-Schrieffer (BCS) theory, an extremely successful framework for understanding conventional superconductors based on the electron-phonon coupling mechanism, cannot explain the pairing mechanism in cuprate superconductors [3]. ...
... The discovery of nickelate superconductors [1][2][3][4] has emerged as a significant milestone in the realm of superconductivity, motivated by the groundbreaking findings of cuprate superconductors since 1986 [5]. Nickelates, with their similar layered perovskite structures to cuprates, have captured the attention of researchers worldwide due to their potential to unveil new insights into unconventional superconducting phenomena [6][7][8][9][10][11][12][13][14][15]. ...
Research on nickel-based superconductors has progressed from infinite-layer LaNiO to finite-layer LaNiO, and most recently to the Ruddlesden-Popper-phase LaNiO discovered under pressure 16\,GPa, the system exhibits the onset of superconductivity at approximately 80\,K. Unlike the d-wave superconductivity driven by the nearly half-filled orbitals in finite- and infinite-layers nickelates, the Ni- and O-2p orbitals contribute significantly to the low energy states and potentially to the superconducting electron pairing mechanism. Employing density functional calculations and multi-orbital multi-atom NiO cluster exact diagonalization including local exchange and coulomb interactions, we delve into the pressure dependent electronic structure of the NiO cluster. We find that several possible charge and spin ordering states are nearly degenerate at ambient pressure but become strongly mixed leading to a more homogeneous phase at high pressure. The various possible spin states and the exchange and superexchange mechanisms are quantified via the involvement of the Ni- orbitals, the apical bridging O orbitals, and the orbitals involved in the formation of local Zhang-Rice singlet like states. We note that the energy difference between the charge (CDW)/spin (SDW) density wave states and the uniform high pressure phase is about 10 meV in concordance with phase transition temperatures found experimentally at ambient pressure.
The discovery of superconductivity in 3d transition‐metal compounds with strong magnetism is interesting but rare. Especially for Mn‐based compounds, there exist only very limited materials that show superconductivity. Here, the discovery of superconductivity is reported with an onset transition temperature up to 14.2 K in a Mn‐based material MnB4, which is the highest value among the stoichiometric Mn‐based superconductors. By applying high pressure, the continuous suppression of a weak semiconducting behavior and the occurrence of superconductivity after ≈30 GPa are found. With further increasing pressure, the superconducting transition temperature (Tc) is gradually enhanced and reaches the maximum onset transition value of ≈14.2 K at 150 GPa. The synchrotron X‐ray diffraction data reveal the unchanged monoclinic (S.G: P21/c) symmetry but an unusual crossover of the lattice parameters b and c in a certain pressure region as confirmed by the theoretical calculation. The findings show a promising way to explore high Tc superconductivity by combining the 3d‐transition metal magnetic elements and light elements.
In recent decades, significant strides have been made in the domain of product innovation and materials technology, especially in the field of electronic devices and sensors. There is immense potential for future materials in electronic-based sensing devices, given their exceptional electrical, magnetic, and optical properties that support the adoption of emerging technologies. In modern electronics, electroceramics is crucial in facilitating new technological advancements. This chapter briefly introduces the importance and role of electroceramic materials in sensor technology. The chapter widely explore the application of various electroceramic materials such as piezoelectric, ferroelectric, semiconductor, solid, Ionic conductors, solid electrolytes thermoelectric, etc., in diverse sensor technologies. The chapter describes the various synthesis methods for electroceramic-based sensing materials. Future perspectives of electrochemical materials for enhancing sensor technology is also highlighted in the chapter.
A novel material is obtained by modifying pristine YBCO superconductor via simultaneous partial substitution of Sr for Ba and Se for O. The intended stoichiometry was [Formula: see text]Sr x Cu 3 [Formula: see text]Se x with [Formula: see text], 0.75 and 1; and [Formula: see text] yielded the most interesting results considered in detail. We confirmed that Se atoms indeed enter the superconductor lattice cell. The obtained polycrystalline material contains five phases, with the major phase ([Formula: see text][Formula: see text]wt.%) being [Formula: see text][Formula: see text]Cu 3 O 6 [Formula: see text]. The synthesized superconductor demonstrates unique properties, including (i) two superconducting transitions with [Formula: see text][Formula: see text]K and [Formula: see text][Formula: see text]K yielding the Wohlleben effect; (ii) strong-coupling d-wave superconductivity (with [Formula: see text] 5); (iii) Schottky anomaly in the heat capacity; and, most importantly, (iv) a very unusual anomaly in the heat capacity which can be associated with the quantum criticality typically observable at much higher fields. The fact that the quantum criticality is visible in weaker fields ([Formula: see text][Formula: see text]T) may open opportunities for exploration of the interplay between superconductivity and pair density waves by wide research community particularly when its pure phase is available. To facilitate this, the stability of single-phase [Formula: see text][Formula: see text]Cu 3 O 6 [Formula: see text] is analyzed using machine learning methods.
In this article, we give the reader a brief introduction to a selected number of smart materials and structures. These materials include semiconductors and related structures, superconductors, piezoelectric materials, and shape memory materials. These materials are discussed in terms of their electrical, mechanical, optical, and chemical properties and possible engineering applications in the fields of nanoelectronics, nano/microelectromechanical systems, optoelectronics, and communication.
Topological magnetic insulators host chiral gapless edge modes. In the presence of strong interaction effects, the spin of these modes may fractionalize. Studying a two-dimensional array of coupled insulating spin- 1 / 2 chains, we show how spatially modulated magnetic fields and Dzyaloshinskii-Moriya interactions can be exploited to realize chiral spin liquids or integer and fractional spin quantum Hall effect phases. These are characterized by a gapped bulk spectrum and gapless chiral edge modes with fractional spin. The spin fractionalization is manifested in the quantized spin conductance, which can be used to probe the fractional spin quantum Hall effect. We analyze the system via bosonization and perturbative renormalization group techniques that allow us to identify the most relevant terms induced by the spin-spin interactions that open gaps and render the system topological under well-specified resonance conditions. We show explicitly that the emerging phase is a genuine chiral spin liquid. We suggest that the phases can be realized experimentally in synthetic spin chains and ultracold atom systems.
Published by the American Physical Society 2024
Recent observations of superconductivity in infinite-layer nickelates offer insights into high-temperature superconductivity mechanisms. However, defects and dislocations in doped films complicate the realization of superconductivity, limiting current research to superconducting nickelate heterostructures. The lack of research on superconductivity in superlattices composed of ultrathin nickelates severely impedes not only the exploration of the interface effect on superconductivity, but also the utilization of heterostructure engineering for exploring higher superconducting temperature Tc. Here, we demonstrated superconducting infinite-layer nickelate superlattices [(Nd0.8Sr0.2NiO2)8/(SrTiO3)2]10 via topotactic reduction. Our study uncovered that only above a critical thickness can high-quality superlattices be achieved, with structural formation dependent on nickelate layer thickness. The superconducting superlattice showed a Tc of 12.5 K and a 2D superconducting feature, indirectly indicate the intrinsic superconductivity of infinite-layer nickelates. Our study offers promising avenues for delving into the superconducting mechanism and for exploring multilevel interface engineering of infinite-layer nickelates, thus opening new horizons for the study of infinite-layer nickelates.
Unconventional high‐temperature superconductivity has long been a captivating puzzle in condensed matter physics. The 1987 Nobel Prize in Physics celebrated the discovery of high‐temperature superconductivity in copper oxide ceramics. Nearly four decades later, a broad class of high‐temperature superconducting oxides has yet to be demonstrated, and the fundamental understanding of the pairing mechanism remains inconclusive. Recently, nickel oxides have emerged as a new class of high‐temperature superconductors, beyond copper, where correlated phases can be controlled by doping, pressure, strain, and dimensionality. In this article, we provide our perspective on the recent developments and prospects of the nickel age of high‐temperature superconductivity.
AC loss estimation in REBCO high-temperature superconductor (HTS) coils is crucial in AC applications. The finite-element method (FEM) modelling is an efficient and widely-used approach to simulate AC loss in HTS coils. However, such models can become time-consuming and resource-intensive due to the high aspect ratio and anisotropic field-angle-dependent critical current properties of REBCO tapes. In addition, HTS coils with complex geometry like saddle-shaped coils, further increase the complexity of models because the 3D rotational asymmetry must be considered. This work presents a detailed demonstration of a 3D 10-turn saddle coil to overcome these simulation challenges. More importantly, the loss behaviors in an HTS saddle coil carrying currents under external magnetic fields are characterized for the first time. Frenet-Serret equations are utilized within the finite element analysis software to construct the 3D structure of a 10-turn saddle coil wound with REBCO tape. The dimensions of the coil are approximately 200 mm in length and 70 mm in width. The T-A formulation is employed, and measured Ic (B,θ) data is interpolated in the FEM model to simulate the electromagnetic behaviors of HTS tapes. The critical current of the saddle coil, along with magnetization loss at various magnetic field amplitudes, dynamic resistance and total loss at different DC current levels, are analyzed. Additionally, a race-track coil model with a similar size to the saddle coil is constructed and simulated for comparison purposes. Simulation results indicate that for both types of coils, the loss is mainly generated in the straight parts rather than the curved end portions.
Motivated by a recent experiment on high-temperature superconductors (Wang Z. C. et al., Nature, 615, (2023) 405), we perform a theoretical study to distinguish the nature of the topological spin texture in the superconducting phase of an underdoped cuprate. We propose a phenomenological tight-binding model of electrons with spin-singlet pairing hopping in the background of topological spin texture on the square lattice to capture the coupling of electrons and the topological spin texture. Two types of topological spin texture relevant to the experiment are considered, i.e., Bloch skyrmion and sinusoidal vortex, and the Bogoliubov-de Gennes mean-field theory is employed to calculate the gap functions and local density of states. We discover an emergent d xy -wave component in the imaginary part of the gap function for skyrmion, but this is not present for vortex. For skyrmion, each coherent peak in the local density of states splits into two spatially uniform peaks, while for vortex, it splits into two spatially modulated peaks. Our study reveals the qualitatively different consequences of two types of topological spin texture, and can be possibly detected in the further STM experiment.
Ever since the discovery of high-temperature superconductivity in cuprates, gaining microscopic insights into the nature of pairing in strongly correlated systems has remained one of the greatest challenges in modern condensed matter physics. Following recent experiments reporting superconductivity in the bilayer nickelate La3Ni2O7 (LNO) with remarkably high critical temperatures of Tc = 80 K, it has been argued that the low-energy physics of LNO can be described by the strongly correlated, mixed-dimensional bilayer t–J model. Here we investigate this bilayer system and utilize density matrix renormalization group techniques to establish a thorough understanding of the model and the magnetically induced pairing through comparison to the perturbative limit of dominating inter-layer spin couplings. In particular, this allows us to explain appearing finite-size effects, firmly establishing the existence of long-range superconducting order in the thermodynamic limit. By analyzing binding energies, we predict a BEC–BCS crossover as a function of the Hamiltonian parameters. We find large binding energies of the order of the inter-layer coupling that suggest strikingly high critical temperatures of the Berezinskii–Kosterlitz–Thouless transition, raising the question of whether (mixD) bilayer superconductors possibly facilitate critical temperatures above room temperature.
Heavy fermion characteristics and potential superconductivity are observed in the partially vacancy-ordered Y 4 Fe x Ge 8 .
Copper oxide high-temperature superconductors, such as Bi2Sr2CaCu2O8+δ (Bi2212), have garnered extensive research interest due to their high critical temperatures (Tc) surpassing the Bardeen–Cooper–Schrieffer (BCS) limit. The two-dimensional CuO₂ plane is widely regarded as the most crucial element of high-Tc cuprate superconductors. The anisotropy of this CuO₂ layer remains a topic of ongoing interest. Although a few experimental results have reported strong optical anisotropy in both ab and ac-planes of Bi2212 through optical “reflectivity” measurements, there is a lack of studies focusing on the optical anisotropy of these materials using optical “transmittance” measurements by utilizing ultraviolet and visible light. Using a generalized high-accuracy universal polarimeter, we observed significant linear birefringence and linear dichroism peaks in the UV region at room temperature. To investigate the origin of the significant optical anisotropy, single crystals of Bi2−xPbxSr2CaCu2O8+δ with different lead contents (x = 0, 0.4, and 0.6) were grown using the floating zone method, and the wavelength dependencies of linear birefringence and linear dichroism along the c axis were measured. The insights gained into the optical anisotropy of Bi2−xPbxSr2CaCu2O8+δ from this study are significant for discussing its origin of the mechanism of high-Tc superconductivity.
Sodium and potassium have been doped into La7SrCu4O16−δ to form La7+2xSr1−4xKxNaxCu4O16−δ solid solutions by a solid-state reaction, which crystallizes in the I4/mmm space group when 0 ≤ x < 0.16 and Fmmm when 0.16 < x ≤ 0.25. With the equivalent replacement of four Sr²⁺ by one Na⁺, one K⁺ and two La³⁺, it is very interesting to find that Tzeroc (the definition is presented in the introduction part) of La7+2xSr1−4xKxNaxCu4O16−δ does not remain constant with an increase in x but first increases from 14.8 K for x = 0.00 to 33.9 K for x = 0.10 and then decreases to 18.5 K for x = 0.175.
The introduction of high-temperature superconductors and, in particular, cuprate oxides such as REBa2Cu3O7–δ (where RE = Y, lanthanides) has led to developments in applied physics and technology. These materials have high technological potential for more economical, smaller magnetically confined fusion reactors due to the high field strengths. The introduction of high-temperature superconductors in the form of tapes in fusion reactors is not technologically trivial as these reactors eject high-energy neutrons that can damage the material and hinder its operation. In the present review, we consider the technological issues that need to be addressed for the implementation of REBa2Cu3O7–δ in fusion reactors.
Layered perovskite-based compounds offer a range of unconventional properties enabled by their naturally anisotropic structure. While most renowned for the superconductivity observed in the Ruddlesden-Popper phases, many of these layered compounds are also ferroelectric and exhibit a sizeable in-plane polarization. Among these, the Carpy-Galy phases (ABO), characterized by 110-oriented perovskite planes interleaved with additional oxygen layers, have been debated as platforms for hosting not only a robust polarization but also multiferroicity and polar metallicity. However, the challenges associated with the synthesis of ultrathin Carpy-Galy films and understanding the impact of strain on their properties limit their integration into devices. Addressing this issue, our study focuses on LaTiO, an n=4 (ABO) representative of the Carpy-Galy family, exploring its growth and concurrent phase stability on various substrates under different strain conditions. Remarkably, we demonstrate that a 3% tensile strain from DyScO (100) substrates promotes a controlled layer-by-layer growth mode, while SrTiO (110) and LaAlO-SrTaAlO (110), that exert negligible and compressive strains respectively, require post-deposition annealing to achieve similar results. Using scanning probe microscopy, X-ray diffraction, scanning transmission electron microscopy, and polarization switching experiments, we confirm that these films possess exceptional ferroelectric properties, including a polarization of 18 C/cm - more than three times higher than previously reported - as well as persistence of ferroelectricity down to a single-unit-cell thickness. This study not only advances our understanding of Carpy-Galy phases in thin films but also lays a foundation for their application in advanced ferroelectric device architectures.
In cuprates, the superconducting transition temperature (Tc) is closely related to the number n of CuO2 planes per unit cell. The studies on multi‐layered cuprates offer insights into the physical properties and pairing mechanisms of superconductivity. However, the synthesis and stability of ultra‐multilayered cuprates pose significant challenges. Here, a newly discovered seven‐layered cuprate CuBa2Ca6Cu7O17±δ grown under high pressure is reported. Magnetization and transport measurements confirm bulk superconductivity with Tc of ≈85 K. The magnetization hysteresis loops, critical current density (Jc), and irreversibility fields of CuBa2Ca6Cu7O17±δ are also investigated. The novel compound CuBa2Ca6Cu7O17±δ provides an ideal platform for studying the physics of multi‐layered cuprates.
A recent experiment by Shan {\it et al} [arXiv:2304.09011] found that rhenium trioxide ReO, a simple metal at the ambient pressure, becomes superconducting with a transition temperature as high as 17 K at 30 GPa. In this paper, we analyze the electron-phonon origin of superconductivity in rhombohedral ReO in detail. In addition, we also conduct a high-throughout screening of isostructural transition-metal trioxides XO in searching for potential pressure-induced superconductors. Totally twenty-eight XO compounds have been studied, in which four candidates RuO, OsO, IrO and PtO are predicted superconducting with the transition temperatures of 26.4, 30.3, 0.9 and 2.8 K at 30 GPa, respectively. Both IrO and PtO stay superconducting even at the ambient pressure. In ReO, RuOOsO and IrO, the conduction electrons around the Fermi level are dominantly from the X-d and the O-2p orbitals, and their electron-phonon coupling originates from the lattice dynamics of both the heavier transition-metal-atom and the oxygen-atom. Inclusion of spin-orbital coupling would mildly suppress the transition temperatures of these transition-metal trioxide superconductors except RuO.
In transverse thermoelectric generators (TTEGs), comprising an artificially anisotropic material formed by a layered and tilted structure of two materials, the induced thermoelectric voltage is generated perpendicular to the applied temperature gradient. The performance of TTEGs composed of alternate layers of La1.99Sr0.01CuO4 (LSCO) and silver (Ag), tilted at an angle φ, with metal‐to‐ceramic thickness ratio νt, is investigated. Improvement in performance is achieved by optimizing the internal geometry parameters, φ and νt of the tilted layered structure. The transverse power factor PFtr and figure‐of‐merit ZtrT of the artificially tilted material composite are analytically calculated and presented in color contours. Experimentally, a power output Pout of 14.5 mW at ΔT = 140 K is measured for a TTEG with φ = 66°, compared to 2.8 mW and 11 mW for generators with φ of 20° and 45°, respectively. Moreover, TTEGs with different values of νt are prepared. Furthermore, transverse multilayer thermoelectric generators (TMLTEG) with output power of 14.3 mW at ΔT = 225 K are fabricated utilizing the ceramic multilayer technology. It is demonstrated that the transverse thermoelectric effect using an artificial anisotropic material consisting of ceramic and metal can be explored for autonomous thermoelectric energy generation for low‐power applications.
Navies have been performing naval ship deperming since World War II. Deperming requires an estimated magnetic field of a few milli-tesla, which is middle in intensity as an artificially generated field. However, the volume required for this magnetic field is as large as the involved ship volume. A concept of flat coil comprising a high-temperature superconducting cable, set on the seabed in shallow water, is expected to have an effective deperming system of a ship. This system requires a magnetic field to overcome the vertical demagnetization of the ship, which is higher than the longitudinal factor. To incorporate a superconducting good performance, we design a coil comprising a present superconductor cooled through liquid hydrogen circulation. Starting from the estimation of the required magnetic field, the cable with 200 kA passing and 1200 m length is discussed, along with the consideration of the liquid hydrogen cooling and required power source for deperming.
We suggest a percolation model for the onset of superconductivity in granular samples. The specific heat and electrical resistance are calculated, and found to be in agreement with experimental data.
Superconducting BaPb 1-xBixO3 thin films were successfully prepared by RF diode sputtering with a relatively high deposition rate of 50–120 A/min and subsequent heat treatments above 500 °C. Their superconducting transition onsets are about 8K. Crystalline films were deposited even at low substrate temperature of about 100 °C, and they had a strong tendency to grow with the orientation (200) of the cubic perovskite structure. It was found that high oxygen partial pressure during discharge is a requisite factor for the preparation of BaPb1-xBixO3 thin films. When oxygen partial pressure is higher, the annealed films have the lower resistivities, the higher superconducting transition temperature and the sharper transitions.
Self-consistent, scalar-relativistic, linear-augmented-plane-wave
electronic-structure calculations have been carried out for the
BaPb1-xBixO3 system in the cubic (x=0,
0.3, 1) and body-centered-tetragonal (x=0.3) phases. The results suggest
that the relatively high superconducting transition temperatures
(Tc~13 K) that are observed for 0.05<=x<=0.3 are due to
strong electron-phonon coupling which arises from modulation of the
dominant (spσ) interaction between neighboring Pb-Bi 6s and O 2p
orbitals at EF.
Superconductivity properties of the BaPb1−x
Bix
O3 system have been investigated by precise measurements of electrical resistivity and Hall coefficient in specimens prepared by the hot press technique. Sharp superconducting transitions have been observed in those specimens, indicating the homogeneities of the specimens thus prepared. superconductivity has been observed for 0.05<x≦0.35 and a maximum critical temperature of 11.7 K has been observed atx=0.25. The carrier concentration deduced from the Hall coefficient has been found to show nearly the samex dependence as does the critical temperature. The upper critical field has been determined from the magnetic field dependence of the lowcurrent-density resistivity. Discussions are given about the superconductivity in the BaPb1−x
Bix
O3 system on the basis of the experiment results.
A new oxygen defect perovskite BaLa4Cu5O13.4, characterized by a mixed valence of copper has been isolated; the parameters of the tetragonal cell are closely related to that of the cubic perovskite:a = 8.644(4) and c = 3.867(3) . The X-ray diffraction study shows that the atoms are displaced from their ideal positions in the cubic cell, owing to the presence of ordered oxygen vacancies. The study of conductivity, magnetic susceptibility and thermoelectric power versus temperature shows that this oxide is a very good metallic conductor.
Mixed LaAlO3-SrTiO3 single crystals have been grown by using flame fusion, starting from homogeneously synthesized solid-solution powders. X-ray powder diffraction of the latter show the solid-solution system to be continuous over the whole composition range. Phase boundaries were determined by means of optical and calorimetric measurements. In the composition range of 100% to 20% LaAlO3, a cubic Pm3m to trigonal R3̄c phase boundary was observed.
The grain boundaries of superconducting BaPb0.7Bi0.3O3 sputtered thin films were found to work as tunnelling barriers and to result in the Josephson effect. The current-voltage characteristics of the films show large hysteresis curves and the Josephson critical current density is two orders of magnitude larger than those ever observed in granular superconducting films of other materials.
Tunneling measurements have been performed on Nb-doped and reduced superconducting SrTiO3. Beyond a certain carrier concentration, when a second conduction band gets filled, a distinctive double-gap structure is observed in Nb-doped samples. Its sharpness and anomalous temperature dependence can be related to the onset of two-band superconductivity in accordance with theoretical expectations. The observation of a single gap Delta~=1.76 kTc in reduced SrTiO3 is attributed to enhanced interband scattering.
Microwave absorption and frequency shift measurements in the normal and in the superconducting state are presented for a metallic type Al-Al2O3 film. The results are explained by simple models using an uniform conductivity for the normal state absorption and percolation ideas for the superconducting transition.
Granular A1 films have been measured in a microwave cavity at 9.4 GHz together with their dc resistance, R(T). The change in resonant frequency is proportional to the number of superconducting electron pairs which is finite above the temperature Tcrho, where R(T)~=0. Microwave loss has been identified which appears to be specific to granular materials and vanishes only well below Tcrho. This is shown to be due to normal conduction between grains, which upon cooling becomes progressively more Josephson-like.
Recent developments in materials research concerned with the physics of
superconductors are reviewed. Consideration is given to the design of
new types of semiconductors including the heavy-fermion liquid
superconductors, low electron-density superconductors and organic and
low dimensional superconductors. More familiar superconducting materials
are also considered including intermetallic A 15 superconductors, B-1
superconductors and amorphous and granular systems. The role of
composite film synthesis in perfecting superconductor fabrication
techniques is briefly discussed.
This is a brief review on how the order parameter symmetry of exotic superconductors may be probed experimentally. Some variants
of experimental techniques employed in searches for evidence of unconventional superconductivity in unusual metals are discussed.
Many independent results indicate that the gap in the electronic excitation spectrum of these superconductors has nodes in
the form of lines or points on the Fermi surface.
Phases of the type BaPb1-xBixO3 have been prepared for the first time. These phases all have perovskite related structures, and superconductivity was observed over the range x ≌ 0.05-0.3. The highest critical temperature is 13 K which is exceptionally high for an oxide and is much higher than that previously observed for any superconductor not containing a transition element. Semiconducting behavior is observed from x = 1 to about 0.35.
The first high temperature superconducting oxide compound is reported. The compound is Li1+xTi2−xO4 and has the face-centered cubic spinel structure, with . The transition temperatures of this compound range from ∼ 7°K to 13.7°K.
A phase diagram is postulated where the ground-state of a strongly coupled electron-phonon system is a bipolaronic insulator beyond a critical coupling strength. This opens up the possibility of phase transition from a superconductor to insulator at T = 0, as the coupling is varied. On propose qu'un système avec un fort couplage électrons-phonons est un isolant bipolaronique au-delà d'une constante de couplage critique. Ceci donne la possibilité d'une transition de phase d'un état supraconducteur à l'état isolant à T = 0 quand on varie la constante de couplage.
Conductivity and density-of-states measurements have been performed on granular Sn films with room-temperature conductivities sigma(300 K) between 1 and 104 Omega-1 cm-1. Our conductivity measurements indicate that superconductivity as well as normal metallic behavior disappear at the metal-insulator transition (sigmac~=40 Omega-1 cm-1). The anomalous magnetoconductivity in the metallic phase is consistent with the scaling picture for the Anderson transition. The temperature dependence of the conductivity is more complex, probably due to the influence of the granular film structure. The importance of the enhanced Coulomb repulsion near the Anderson transition is directly reflected by the appearance of a square-root anomaly in the density of states around the Fermi level. The granularity of the Sn films causes this anomaly to be considerably smaller than for homogeneous amorphous metals.
In: Superconductivity ind- andf-Band Metals, Proceedings IV Conference in ‘Superconductivity ind- andf-Band Metals
- A Baratoff
- G Binnig
- A Baratoff
- G Binnig
- J G Bednorz
- F Gervais
- J L Servoin
Magnetic and other properties of oxide and related compounds In: Landolt-Boernstein New Series Vol III/4a: Crystal and solid state physics
- J.B. Goodenough