Effects of Excess or Deficiency of Oxygen Content on the Electronic Structure of High-T c Cuprates

Jarlborg, T.; Bianconi, A.; Barbiellini, B.; Markiewicz, R. S.; Bansil, Arun

doi:10.1007/s10948-013-2142-3

Cited by 12 publications

(11 citation statements)

References 31 publications

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“…From the electronic contribution to the specific heat, γ el , the electronic DoS at the Fermi level in a freeelectron model is obtained as N (E F ) = 17.8 states/(eV unit cell). This value should be compared to N (E F ) = 9.6 states/(eV unit cell) obtained from spin-polarized LDA band calculations 53 . Taking a reasonable estimate for the electron-phonon coupling λ = 0.2 into account 53 results in γ el = 1 3 π 2 k 2 B N (E F )(1 + λ) ≈ 7 mJ/(mol K 2 ).…”

Section: B Specific Heat and Thermal Expansionmentioning

confidence: 97%

Scaling study and thermodynamic properties of the cubic helimagnet FeGe

et al. 2016

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The critical behavior of the cubic helimagnet FeGe was obtained from isothermal magnetization data in very close vicinity of the ordering temperature. A thorough and consistent scaling analysis of these data revealed the critical exponents β = 0.368, γ = 1.382, and δ = 4.787. The anomaly in the specific heat associated with the magnetic ordering can be well described by the critical exponent α = −0.133. The values of these exponents corroborate that the magnetic phase transition in FeGe belongs to the isotropic 3D-Heisenberg universality class. The specific heat data are well described by ab initio phonon calculations and confirm the localized character of the magnetic moments.

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Section: B Specific Heat and Thermal Expansionmentioning

confidence: 97%

Scaling study and thermodynamic properties of the cubic helimagnet FeGe

et al. 2016

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“…The origin of the unusual physical properties, such as Kondo and heavy fermion behaviour, of some cerium compounds. 34,35 is believed to be due to an unusual 4f density of states peak at the Fermi level 36 depending on the onsite electron correlations. The calculations with reduced Hubbard U parameter (e.g., for U = 3 eV) indicate that the double peak 4f DOS in CeRhAl 4 Si 2 and CeIrAl 4 Si 2 and single peak 4f DOS in CePtAl 4 Si 2 (seen with U = 6.7 eV) shift towards the Fermi level (without significantly affecting the unoccupied 4f DOS) altering their coupling to the conduction electrons close to the Fermi level.…”

Section: G Electronic Structurementioning

confidence: 99%

Kondo Lattice and Antiferromagnetic Behavior in Quaternary CeTAl₄Si₂ (T = Rh, Ir) Single Crystals

et al. 2016

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We report the synthesis and the magnetic properties of single crystalline CeRhAl4Si2 and CeIrAl4Si2 and their non magnetic La-analogs. The single crystals of these quaternary compounds were grown using Al-Si binary eutectic as flux. The anisotropic magnetic properties of the cerium compounds were explored in detail by means of magnetic susceptibility, isothermal magnetization, electrical resistivity at ambient and applied pressures up to 12.6 kbar, magnetoresistivity and heat capacity measurements. Both CeRhAl4Si2 and CeIrAl4Si2 undergo two antiferromagnetic transitions, first from the paramagnetic to an antiferromagnetic state at TN1 = 12.6 K and 15.5 K, followed by a second transition at lower temperatures TN2 = 9.4 K and 13.8 K (inferred from the peaks in the heat capacity), respectively, in conformity with an earlier report in the literature. The paramagnetic susceptibility is highly anisotropic and its temperature dependence in the magnetically ordered state suggests the c-axis to be the relatively easy axis of magnetization. Concomitantly, isothermal magnetization at 2 K along the c-axis shows a sharp spin-flop transition accompanied by a sizeable hysteresis, while it varies nearly linearly with field along the [100] direction up to the highest field 14 T of our measurement. The electrical resistivity provides evidence of the Kondo interaction in both compounds, inferred from its −lnT behavior in the paramagnetic region and the decrease of magnetic transition temperature with pressure. The heat capacity data confirm the bulk nature of the two magnetic transitions in each compound, and further support the presence of Kondo interaction by a reduced value of the entropy associated with the magnetic ordering. From the heat capacity data below 1 K, the coefficient of the linear term in the electronic heat capacity, γ, is inferred to be 195.6 and 49.4 mJ/mol K 2 in CeRhAl4Si2 and CeIrAl4Si2, respectively classifying these materials as moderate heavy fermion compounds. The main features of the magnetoresistivity measured at a particular temperature correlate nicely with the isothermal magnetization at the same temperature in these two isostructural compounds. We have also carried out an analysis of the magnetization based on the point charge crystal electric field model and derived the crystal electric field energy levels which reproduce fairly well the peak seen in the Schottky heat capacity in the paramagnetic region. Further, we have also performed electronic structure calculations using (LSDA +U) approach, which provide physical insights on the observed magnetic behaviour of these two compounds.

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“…Optic modes in underdoped cuprates are not efficient for long-range superconductivity, but acoustic modes grow in importance at higher doping. electronic interplane interaction is reduced in the former material because of less apical oxygens, and it makes the FS even more flat at optimal doping than in La 2 CuO 4 [44,48,49]. Additional ordering of dopants into static stripes has been suggested to lead to a segmentation of the FS and enhanced T C [50][51][52].…”

Section: Cupratesmentioning

confidence: 99%

Electronic Structure and Properties of Superconducting Materials with Simple Fermi Surfaces

Jarlborg

2014

J Supercond Nov Magn

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The electronic structures of the ground state for several different superconducting materials, such as cuprates, conventional 3-dimensional superconductors, doped semiconductors and lowdimensional systems, are quite different and sometimes in contrast to what is supposed to make a superconductor. Properties like the Fermi-surface (FS) topology, density-of-states (DOS), stripes, electron-phonon coupling (λep) and spin fluctuations (λ sf ) are analyzed in order to find clues to what might be important for the mechanism of superconductivity. A high DOS at EF is important for standard estimates of λ ′ s, but it is suggested that superconductivity can survive a low DOS if the FS is simple enough. Superconducting fluctuations are plausible from coupling to long wave length modes in underdoped cuprates, where short coherence length is a probable obstacle for long-range superconductivity. Thermal disorder is recognized as a limiting factor for large TC independently of doping.

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Effects of Excess or Deficiency of Oxygen Content on the Electronic Structure of High-T c Cuprates

Cited by 12 publications

References 31 publications

Scaling study and thermodynamic properties of the cubic helimagnet FeGe

Scaling study and thermodynamic properties of the cubic helimagnet FeGe

Kondo Lattice and Antiferromagnetic Behavior in Quaternary CeTAl₄Si₂ (T = Rh, Ir) Single Crystals

Electronic Structure and Properties of Superconducting Materials with Simple Fermi Surfaces

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Effects of Excess or Deficiency of Oxygen Content on the Electronic Structure of High-T c Cuprates

Cited by 12 publications

References 31 publications

Scaling study and thermodynamic properties of the cubic helimagnet FeGe

Scaling study and thermodynamic properties of the cubic helimagnet FeGe

Kondo Lattice and Antiferromagnetic Behavior in Quaternary CeTAl4Si2 (T = Rh, Ir) Single Crystals

Electronic Structure and Properties of Superconducting Materials with Simple Fermi Surfaces

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Product

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Kondo Lattice and Antiferromagnetic Behavior in Quaternary CeTAl₄Si₂ (T = Rh, Ir) Single Crystals