Sign in to use this feature.

Years

Between: -

Subjects

remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline

Journals

Article Types

Countries / Regions

Search Results (26)

Search Parameters:
Keywords = electron-doped cuprates

Order results
Result details
Results per page
Select all
Export citation of selected articles as:
12 pages, 3225 KiB  
Article
Multiple Slater Determinants and Strong Spin-Fluctuations as Key Ingredients of the Electronic Structure of Electron- and Hole-Doped Pb10−xCux(PO4)6O
by Dimitar Pashov, Swagata Acharya, Stephan Lany, Daniel S. Dessau and Mark van Schilfgaarde
Crystals 2025, 15(7), 621; https://doi.org/10.3390/cryst15070621 - 2 Jul 2025
Viewed by 953
Abstract
LK-99, with chemical formula Pb10−xCux(PO4)6O, was recently reported to be a room-temperature superconductor. While this claim has met with little support in a flurry of ensuing work, a variety of calculations (mostly based on [...] Read more.
LK-99, with chemical formula Pb10−xCux(PO4)6O, was recently reported to be a room-temperature superconductor. While this claim has met with little support in a flurry of ensuing work, a variety of calculations (mostly based on density-functional theory) have demonstrated that the system possesses some unusual characteristics in the electronic structure, in particular flat bands. We have established previously that within DFT, the system is insulating with many characteristics resembling the classic cuprates, provided the structure is not constrained to the P3(143) symmetry nominally assigned to it. Here we describe the basic electronic structure of LK-99 within self-consistent many-body perturbative approach, quasiparticle self-consistent GW (QSGW) approximation and their diagrammatic extensions. QSGW predicts that pristine LK-99 is indeed a Mott/charge transfer insulator, with a bandgap gap in excess of 3 eV, whether or not constrained to the P3(143) symmetry. When Pb9Cu(PO4)6O is hole-doped, the valence bands modify only slightly, and a hole pocket appears. However, two solutions emerge: a high-moment solution with the Cu local moment aligned parallel to neighbors, and a low-moment solution with Cu aligned antiparallel to its environment. In the electron-doped case the conduction band structure changes significantly: states of mostly Pb character merge with the formerly dispersionless Cu d state, and high-spin and low spin solutions once again appear. Thus we conclude that with suitable doping, the ground state of the system is not adequately described by a band picture, and that strong correlations are likely. Irrespective of whether this system class hosts superconductivity or not, the transition of Pb10(PO4)6O from being a band insulator to Pb9Cu(PO4)6O, a Mott insulator, and multi-determinantal nature of doped Mott physics make this an extremely interesting case-study for strongly correlated many-body physics. Full article
Show Figures

Figure 1

7 pages, 1325 KiB  
Article
The Electron–Phonon Interaction in Non-Stoichiometric Bi2Sr2CaCu2O8+δ Superconductor Obtained from the Diffuse Elastic Scattering of Helium Atoms
by Giorgio Benedek, Joseph R. Manson, Salvador Miret-Artés, Detlef Schmicker and Jan Peter Toennies
Condens. Matter 2024, 9(4), 51; https://doi.org/10.3390/condmat9040051 - 25 Nov 2024
Viewed by 1104
Abstract
Previously, helium atom scattering (HAS) has been shown to probe the electron–phonon interaction at conducting crystal surfaces via the temperature dependence of the specular peak intensity. This method is now extended to non-stoichiometric superconductors. The electron–phonon interaction, as expressed by the mass-enhancement factor [...] Read more.
Previously, helium atom scattering (HAS) has been shown to probe the electron–phonon interaction at conducting crystal surfaces via the temperature dependence of the specular peak intensity. This method is now extended to non-stoichiometric superconductors. The electron–phonon interaction, as expressed by the mass-enhancement factor λ, is derived from the temperature dependence of the diffuse elastic scattering intensity, which specifically depends on the non-stoichiometric component responsible for superconductivity. The measured value of the mass-enhancement factor for Bi2Sr2CaCu2O8+δ at the optimal doping δ = 0.16 is λ = 0.55 ± 0.08 is in good agreement with values of λ recently estimated with other methods. This also confirms the relevant role of electron–phonon interaction in high-temperature non-stoichiometric cuprate superconductors. Full article
(This article belongs to the Special Issue Complexity in Quantum Materials: In Honor of Prof. K.A. Muller)
Show Figures

Figure 1

11 pages, 543 KiB  
Article
A Theoretical Study of Doping Evolution of Phonons in High-Temperature Cuprate Superconductors
by Saheli Sarkar
Condens. Matter 2024, 9(1), 13; https://doi.org/10.3390/condmat9010013 - 6 Feb 2024
Cited by 1 | Viewed by 2460
Abstract
Hole-doped high-temperature copper oxide-based superconductors (cuprates) exhibit complex phase diagrams where electronic orders like a charge density wave (CDW) and superconductivity (SC) appear at low temperatures. The origins of these electronic orders are still open questions due to their complex interplay and correlated [...] Read more.
Hole-doped high-temperature copper oxide-based superconductors (cuprates) exhibit complex phase diagrams where electronic orders like a charge density wave (CDW) and superconductivity (SC) appear at low temperatures. The origins of these electronic orders are still open questions due to their complex interplay and correlated nature. These electronic orders can modify the phonons in the system, which has also been experimentally found in several cuprates as a softening in the phonon frequency at the CDW vector. Recent experiments have revealed that the softening in phonons in cuprates due to CDW shows intriguing behavior with increasing hole doping. Hole doping can also change the underlying Fermi surface. Therefore, it is an interesting question whether the doping-induced change in the Fermi surface can affect the softening of phonons, which in turn can reveal the nature of the electronic orders present in the system. In this work, we investigate this question by studying the softening of phonons in the presence of CDW and SC within a perturbative approach developed in an earlier work. We compare the results obtained within the working model to some experiments. Full article
(This article belongs to the Special Issue Superstripes Physics, 2nd Edition)
Show Figures

Figure 1

11 pages, 1687 KiB  
Article
Dynamic Correlations in Disordered Systems: Implications for High-Temperature Superconductivity
by Takeshi Egami
Condens. Matter 2024, 9(1), 12; https://doi.org/10.3390/condmat9010012 - 3 Feb 2024
Viewed by 2264
Abstract
Liquids and gases are distinct in their extent of dynamic atomic correlations; in gases, atoms are almost uncorrelated, whereas they are strongly correlated in liquids. This distinction applies also to electronic systems. Fermi liquids are actually gas-like, whereas strongly correlated electrons are liquid-like. [...] Read more.
Liquids and gases are distinct in their extent of dynamic atomic correlations; in gases, atoms are almost uncorrelated, whereas they are strongly correlated in liquids. This distinction applies also to electronic systems. Fermi liquids are actually gas-like, whereas strongly correlated electrons are liquid-like. Doped Mott insulators share characteristics with supercooled liquids. Such distinctions have important implications for superconductivity. We discuss the nature of dynamic atomic correlations in liquids and a possible effect of strong electron correlations and Bose–Einstein condensation on the high-temperature superconductivity of the cuprates. Full article
(This article belongs to the Special Issue Superstripes Physics, 2nd Edition)
Show Figures

Figure 1

16 pages, 6994 KiB  
Article
Point-Contact Spectroscopy in Bulk Samples of Electron-Doped Cuprate Superconductors
by Angela Nigro, Anita Guarino, Antonio Leo, Gaia Grimaldi, Francesco Avitabile and Paola Romano
Materials 2023, 16(24), 7644; https://doi.org/10.3390/ma16247644 - 14 Dec 2023
Cited by 1 | Viewed by 1541
Abstract
Point-contact spectroscopy was performed on bulk samples of electron-doped high temperature superconductor Nd2−xCexCuO4−δ. The samples were characterized using X-ray diffraction and scanning electron microscopy equipped with a wavelength-dispersive spectrometer and an electron backscatter diffraction detector. Samples with [...] Read more.
Point-contact spectroscopy was performed on bulk samples of electron-doped high temperature superconductor Nd2−xCexCuO4−δ. The samples were characterized using X-ray diffraction and scanning electron microscopy equipped with a wavelength-dispersive spectrometer and an electron backscatter diffraction detector. Samples with Ce content x = 0.15 showed the absence of spurious phases and randomly oriented grains, most of which had dimensions of approximately 220 µm2. The low-bias spectra in the tunneling regime, i.e., high-transparency interface, exhibited a gap feature at about ±5 meV and no zero-bias conductance, despite the random oriented grains investigated within our bulk samples, consistent with most of the literature data on oriented samples. High-bias conductance was also measured in order to obtain information on the properties of the barrier. A V-shape was observed in some cases, instead of the parabolic behavior expected for tunnel junctions. Full article
(This article belongs to the Special Issue Physics and Application of Superconductivity)
Show Figures

Figure 1

9 pages, 1996 KiB  
Article
The Evaluation of the Crystal Structure and Magnetic Properties of Eu1.84Ce0.16CuO4+α−δ with Ni Substitution
by Muhammad Fadhil Falhan, Rosaldi Pratama, Lucia Patia Rochman, Rahma Sundaya Effendi, Yati Maryati, Utami Widyaiswari, Dita Puspita Sari, Togar Saragi and Risdiana Risdiana
Crystals 2023, 13(7), 1066; https://doi.org/10.3390/cryst13071066 - 6 Jul 2023
Cited by 2 | Viewed by 1661
Abstract
The addition of Ni impurities can reveal the correlation between crystal structure changes and magnetic properties and superconductivity. In this study, electron-doped cuprates with an addition of the Eu1.84Ce0.16Cu1−yNiyO4+α−δ (ECCNO) Ni impurity, with y [...] Read more.
The addition of Ni impurities can reveal the correlation between crystal structure changes and magnetic properties and superconductivity. In this study, electron-doped cuprates with an addition of the Eu1.84Ce0.16Cu1−yNiyO4+α−δ (ECCNO) Ni impurity, with y = 0.005, 0.01, 0.02, 0.03, and 0.05 in the over-doped regime, was prepared using the solid-state reaction method. The XRD results showed that ECCNO has a T’ crystal structure, and lattice parameter c increases when parameters a and b decrease, which causes the distance between the charge reservoir and the conducting layer to become greater, thus affecting magnetic properties. From the superconducting quantum interference device’s measurement, it was observed that the magnetic properties of all samples with Ni impurities show a paramagnetic phase, indicating that the effect of Ni impurities could suppress the superconducting phase. It was observed that the Curie constant and the effective magnetic moment tended to decrease for y ≤ 0.02 and began to increase when y > 0.02. This behavior indicated that the effect of the Ni impurity weakened the dynamical Cu spin–spin correlation, which might be related to stripe correlations. Full article
(This article belongs to the Special Issue Advances in Intermetallic and Metal-Like Compounds)
Show Figures

Figure 1

10 pages, 1900 KiB  
Article
Tc Saturation and Possible Electronic Phase Separation in Strongly Overdoped Cuprates
by Amirreza Hemmatzade, Elena Medina, Ludovic Delbes, Benoît Baptiste, David Hrabovsky, Yannick Klein, Steven D. Conradson, Maarit Karppinen and Andrea Gauzzi
Condens. Matter 2023, 8(3), 56; https://doi.org/10.3390/condmat8030056 - 5 Jul 2023
Viewed by 1630
Abstract
In order to elucidate the unusual superconducting properties of cuprates in the strongly overdoped region, i.e., at hole-doping levels p0.4/Cu in the CuO2 plane, we study the structural and superconducting properties of a series of Cu0.75Mo0.25 [...] Read more.
In order to elucidate the unusual superconducting properties of cuprates in the strongly overdoped region, i.e., at hole-doping levels p0.4/Cu in the CuO2 plane, we study the structural and superconducting properties of a series of Cu0.75Mo0.25Sr2YCu2O7+x powder samples oxygenated under high pressure using different concentrations of KClO3 up to 35 mol %. The analysis of X-ray diffraction data indicates a high purity ∼90% of all samples and suggests that the concentration, x, of extra oxygen atoms increases with increasing KClO3 concentration. Surprisingly, the Tc values remain nearly constant within the 80–85 K range independent of KClO3 concentration, which suggests a scenario of Tc saturation. In order to account for this unexpected behaviour, we put forward the hypothesis that overdoping enhances the density of unpaired holes, which is supported by the observation of large values of the Sommerfeld coefficient in all samples. We therefore propose a scenario of electronic phase separation between normal and superconducting holes. Full article
(This article belongs to the Special Issue Superstripes Physics)
Show Figures

Figure 1

15 pages, 3276 KiB  
Article
One- and Two-Particle Correlation Functions in the Cluster Perturbation Theory for Cuprates
by Valerii I. Kuz’min, Sergey V. Nikolaev, Maxim M. Korshunov and Sergey G. Ovchinnikov
Materials 2023, 16(13), 4640; https://doi.org/10.3390/ma16134640 - 27 Jun 2023
Cited by 5 | Viewed by 1403
Abstract
The physics of high-Tc superconducting cuprates is obscured by the effect of strong electronic correlations. One way to overcome this problem is to seek an exact solution at least within a small cluster and expand it to the whole crystal. Such [...] Read more.
The physics of high-Tc superconducting cuprates is obscured by the effect of strong electronic correlations. One way to overcome this problem is to seek an exact solution at least within a small cluster and expand it to the whole crystal. Such an approach is at the heart of cluster perturbation theory (CPT). Here, we developed CPT for the dynamic spin and charge susceptibilities (spin-CPT and charge-CPT), with the correlation effects explicitly taken into account by the exact diagonalization. We applied spin-CPT and charge-CPT to the effective two-band Hubbard model for the cuprates obtained from the three-band Emery model and calculated one- and two-particle correlation functions, namely, a spectral function and spin and charge susceptibilities. The doping dependence of the spin susceptibility was studied within spin-CPT and CPT-RPA, that is, the CPT generalization of the random phase approximation (RPA). In the underdoped region, both our methods resulted in the signatures of the upper branch of the spin excitation dispersion with the lowest excitation energy at the (π,π) wave vector and no presence of low-energy incommensurate excitations. In the high doping region, both methods produced a low energy response at four incommensurate wave vectors in qualitative agreement with the results of the inelastic neutron scattering experiments on overdoped cuprates. Full article
Show Figures

Figure 1

14 pages, 1515 KiB  
Article
Quantifying Nonadiabaticity in Major Families of Superconductors
by Evgueni F. Talantsev
Nanomaterials 2023, 13(1), 71; https://doi.org/10.3390/nano13010071 - 23 Dec 2022
Cited by 9 | Viewed by 2427
Abstract
The classical Bardeen–Cooper–Schrieffer and Eliashberg theories of the electron–phonon-mediated superconductivity are based on the Migdal theorem, which is an assumption that the energy of charge carriers, kBTF, significantly exceeds the phononic energy, ωD, of the crystalline [...] Read more.
The classical Bardeen–Cooper–Schrieffer and Eliashberg theories of the electron–phonon-mediated superconductivity are based on the Migdal theorem, which is an assumption that the energy of charge carriers, kBTF, significantly exceeds the phononic energy, ωD, of the crystalline lattice. This assumption, which is also known as adiabatic approximation, implies that the superconductor exhibits fast charge carriers and slow phonons. This picture is valid for pure metals and metallic alloys because these superconductors exhibit ωDkBTF<0.01. However, for n-type-doped semiconducting SrTiO3, this adiabatic approximation is not valid, because this material exhibits ωDkBTF50. There is a growing number of newly discovered superconductors which are also beyond the adiabatic approximation. Here, leaving aside pure theoretical aspects of nonadiabatic superconductors, we classified major classes of superconductors (including, elements, A-15 and Heusler alloys, Laves phases, intermetallics, noncentrosymmetric compounds, cuprates, pnictides, highly-compressed hydrides, and two-dimensional superconductors) by the strength of nonadiabaticity (which we defined by the ratio of the Debye temperature to the Fermi temperature, TθTF). We found that the majority of analyzed superconductors fall into the 0.025TθTF0.4 band. Based on the analysis, we proposed the classification scheme for the strength of nonadiabatic effects in superconductors and discussed how this classification is linked with other known empirical taxonomies in superconductivity. Full article
(This article belongs to the Special Issue Superconducting Nanostructures and Materials)
Show Figures

Figure 1

14 pages, 1472 KiB  
Article
Moiré-like Superlattice Generated van Hove Singularities in a Strained CuO2 Double Layer
by Artem O. Sboychakov, Kliment I. Kugel and Antonio Bianconi
Condens. Matter 2022, 7(3), 50; https://doi.org/10.3390/condmat7030050 - 23 Aug 2022
Cited by 3 | Viewed by 2302
Abstract
While it is known that the double-layer Bi2Sr2CaCu2O8+y (BSCCO) cuprate superconductor exhibits a one-dimensional (1D) incommensurate superlattice (IS), the effect of IS on the electronic structure remains elusive. Following the recent shift of interest [...] Read more.
While it is known that the double-layer Bi2Sr2CaCu2O8+y (BSCCO) cuprate superconductor exhibits a one-dimensional (1D) incommensurate superlattice (IS), the effect of IS on the electronic structure remains elusive. Following the recent shift of interest from an underdoped phase to optimum and overdoped phases in BSCCO by increasing the hole doping x, controlled by the oxygen interstitials concentration y, here we focus on the multiple splitting of the density of states (DOS) peaks and emergence of higher order van Hove singularities (VHS) due to the 1D incommensurate superlattice. It is known that the 1D incommensurate wave vector q=ϵb (where b is the reciprocal lattice vector of the orthorhombic lattice) is controlled by the misfit strain between different atomic layers in the range 0.2090.215 in BSCCO and in the range 0.2090.25 in Bi2Sr2Ca1xYxCu2O8+y (BSCYCO). This work reports the theoretical calculation of a complex pattern of VHS due to the 1D incommensurate superlattice with large 1D quasi-commensurate supercells with the wave vector ϵ=9/η in the range 36>η>43. The similarity of the complex VHS splitting and appearing of higher order VHS in a mismatched CuO2 bilayer with VHS due to the moiré lattice in strained twisted bilayer graphene is discussed. This makes a mismatched CuO2 bilayer quite promising for constructing quantum devices with tuned physical characteristics. Full article
(This article belongs to the Section Superconductivity)
Show Figures

Figure 1

10 pages, 3725 KiB  
Article
Changes in the Structural Parameters and Effective Magnetic Moment of Eu2−xCexCuO4+α−δ by Zn Substitution
by Rosaldi Pratama, Togar Saragi, Trisna Maulana, Suci Winarsih, Yati Maryati, Muhammad Abdan Syakuur, Utami Widyaiswari, Dita Puspita Sari, Maykel Manawan and Risdiana Risdiana
Coatings 2022, 12(6), 789; https://doi.org/10.3390/coatings12060789 - 7 Jun 2022
Cited by 10 | Viewed by 2127
Abstract
The effect of nonmagnetic Zn impurities on the structural parameters and effective magnetic moment of electron-doped superconducting cuprates Eu2−xCexCu1−yZnyO4+αδ (ECCZO) with x = 0.10 and 0.15 and y = 0 [...] Read more.
The effect of nonmagnetic Zn impurities on the structural parameters and effective magnetic moment of electron-doped superconducting cuprates Eu2−xCexCu1−yZnyO4+αδ (ECCZO) with x = 0.10 and 0.15 and y = 0 and 0.01 has been investigated using XRD and SQUID measurements. From XRD measurements, it is found that the lattice parameter of c and the Cu-O bond length increase with increasing y. The crystallite size of ECCZO samples was relatively smaller than the sample without impurities determined by the Debye–Scherrer equation and the W-H Plot method. Changes in the lattice parameters of c and Cu-O bond length can affect the appearance of superconductivity (Tc). The smaller the value of the lattice parameter of c and the Cu-O bond length causes the distance between the conducting layer and the charge reservoir to be close enough so that the charge transfer process becomes easier. From the magnetic susceptibility measurement, paramagnetic characteristics were observed for samples with x = 0.10. Meanwhile, for samples with x = 0.15, diamagnetic characteristics can be identified in sample with y = 0. The onset of Tc was observed around 11 K, as indicated by a change from paramagnetic to diamagnetic characteristics. The superconductivity phase disappears with y = 0.01. The effective magnetic moments in samples with y = 0 are smaller than those in samples with y = 0.01. The effective magnetic moment in ECCZO can be contributed by Cu2+. When the amount of Cu2+ decreases due to the addition of nonmagnetic Zn2+ atoms, the overall effective magnetic moment value also decreases. Another possibility that causes a decrease in the value of the magnetic moment of the ECCZO is the existence of stripe-pinning model, which results in suppressed superconductivity by Zn. Full article
(This article belongs to the Special Issue New Advance in Superconductor and Superconducting Thin Films)
Show Figures

Figure 1

10 pages, 1853 KiB  
Article
Normal-State Transport Properties of Infinite-Layer Sr1−xLaxCuO2 Electron-Doped Cuprates in Optimal- and Over-Doped Regimes
by Pasquale Orgiani, Alice Galdi, Darrell G. Schlom and Luigi Maritato
Nanomaterials 2022, 12(10), 1709; https://doi.org/10.3390/nano12101709 - 17 May 2022
Cited by 1 | Viewed by 2312
Abstract
Transport properties of electron-doped cuprate Sr1xLaxCuO2 thin films have been investigated as a function of doping. In particular, optimal- and over-doped samples were obtained by tuning the Sr:La stoichiometric ratio. Optimal-doped samples show a non-Fermi liquid [...] Read more.
Transport properties of electron-doped cuprate Sr1xLaxCuO2 thin films have been investigated as a function of doping. In particular, optimal- and over-doped samples were obtained by tuning the Sr:La stoichiometric ratio. Optimal-doped samples show a non-Fermi liquid behavior characterized by linear dependence of the resistivity from room temperature down to intermediate temperature (about 150–170 K). However, by approaching temperatures in the superconducting transition, a Fermi-liquid behavior-characterized by a T2-scaling law-was observed. Once established, the transition from a linear-T to a quadratic-T2 behavior was successfully traced back in over-doped samples, even occurring at lower temperatures. In addition, the over-doped samples show a crossover to a linear-T to a logarithmic dependence at high temperatures compatible with anti-ferromagnetic spin fluctuations dominating the normal state properties of electron-doped cuprates. Full article
Show Figures

Figure 1

8 pages, 1701 KiB  
Article
Comparing Thickness and Doping-Induced Effects on the Normal States of Infinite-Layer Electron-Doped Cuprates: Is There Anything to Learn?
by Chiara Sacco, Alice Galdi, Francesco Romeo, Nunzia Coppola, Pasquale Orgiani, Haofei I. Wei, Kyle M. Shen, Darrell G. Schlom and Luigi Maritato
Nanomaterials 2022, 12(7), 1092; https://doi.org/10.3390/nano12071092 - 26 Mar 2022
Cited by 1 | Viewed by 2485
Abstract
We grew Sr1-xLaxCuO2 thin films and SrCuO2/Sr0.9La0.1CuO2/SrCuO2 trilayers by reflection high-energy diffraction-calibrated layer-by-layer molecular beam epitaxy, to study their electrical transport properties as a function of the doping and [...] Read more.
We grew Sr1-xLaxCuO2 thin films and SrCuO2/Sr0.9La0.1CuO2/SrCuO2 trilayers by reflection high-energy diffraction-calibrated layer-by-layer molecular beam epitaxy, to study their electrical transport properties as a function of the doping and thickness of the central Sr0.9La0.1CuO2 layer. For the trilayer samples, as already observed in underdoped SLCO films, the electrical resistivity versus temperature curves as a function of the central layer thickness show, for thicknesses thinner than 20 unit cells, sudden upturns in the low temperature range with the possibility for identifying, in the normal state, the T* and a T** temperatures, respectively, separating high-temperature linear behavior and low-temperature quadratic dependence. By plotting the T* and T** values as a function of TConset for both the thin films and the trilayers, the data fall on the same curves. This result suggests that, for the investigated trilayers, the superconducting critical temperature is the important parameter able to describe the normal state properties and that, in the limit of very thin central layers, such properties are mainly influenced by the modification of the energy band structure and not by interface-related disorder. Full article
Show Figures

Figure 1

11 pages, 564 KiB  
Article
Character of Doped Holes in Nd1−xSrxNiO2
by Tharathep Plienbumrung, Michael Thobias Schmid, Maria Daghofer and Andrzej M. Oleś
Condens. Matter 2021, 6(3), 33; https://doi.org/10.3390/condmat6030033 - 19 Aug 2021
Cited by 6 | Viewed by 3757
Abstract
We investigate charge distribution in the recently discovered high-Tc superconductors, layered nickelates. With increasing value of charge-transfer energy, we observe the expected crossover from the cuprate to the local triplet regime upon hole doping. We find that the dp [...] Read more.
We investigate charge distribution in the recently discovered high-Tc superconductors, layered nickelates. With increasing value of charge-transfer energy, we observe the expected crossover from the cuprate to the local triplet regime upon hole doping. We find that the dp Coulomb interaction Udp makes Zhang-Rice singlets less favorable, while the amplitude of local triplets at Ni ions is enhanced. By investigating the effective two-band model with orbitals of x2y2 and s symmetries we show that antiferromagnetic interactions dominate for electron doping. The screened interactions for the s band suggest the importance of rare-earth atoms in superconducting nickelates. Full article
(This article belongs to the Special Issue Quantum Complex Matter from Charge Density Waves to Superstripes)
Show Figures

Figure 1

12 pages, 6127 KiB  
Article
First-Principles Calculation of Copper Oxide Superconductors That Supports the Kamimura-Suwa Model
by Hiroshi Kamimura, Masaaki Araidai, Kunio Ishida, Shunichi Matsuno, Hideaki Sakata, Kenji Shiraishi, Osamu Sugino and Jaw-Shen Tsai
Condens. Matter 2020, 5(4), 69; https://doi.org/10.3390/condmat5040069 - 2 Nov 2020
Cited by 4 | Viewed by 4230
Abstract
In 1986 Bednorz and Műller discovered high temperature superconductivity in copper oxides by chemically doping holes into La2CuO4 (LCO), the antiferromagnetic insulator. Despite intense experimental and theoretical research during the past 34 years, no general consensus on the electronic-spin structures [...] Read more.
In 1986 Bednorz and Műller discovered high temperature superconductivity in copper oxides by chemically doping holes into La2CuO4 (LCO), the antiferromagnetic insulator. Despite intense experimental and theoretical research during the past 34 years, no general consensus on the electronic-spin structures and the origin of pseudogap has been obtained. In this circumstance, we performed a first-principles calculation of underdoped cuprate superconductors La2-xSrxCuO4 (LSCO) within the meta-generalized gradient approximation of the density functional theory. Our calculations clarify first the important role of the anti Jahn-Teller (JT) effect, the backward deformation against the JT distortion in La2CuO4 by doping extra holes. The resulting electronic structure agrees with the two-component theory provided by the tight-binding model of Kamimura and Suwa (K-S), which has been also used to elucidate the d-wave superconductivity. Our first-principles calculation thus justifies the K-S model and demonstrates advanced understanding of cuprates. For example, the remarkable feature of our calculations is the appearance of the spin-polarized band with a nearly flat-band character, showing the peaky nature in the density of states at the Fermi level. Full article
Show Figures

Figure 1

Back to TopTop