Coexistence of the superconducting energy gap and pseudogap above and below the transition temperature of cuprate superconductors

Tallon, J. L.; Barber, Felix; Storey, J. G.; Loram, J. W.

doi:10.1103/physrevb.87.140508

Cited by 34 publications

(48 citation statements)

References 26 publications

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“…This means that in the temperature range from T mf c up to T 01 , FCPs behave in a good many way like superconducting, but incoherent pairs (short-range phase correlations [2,3,8,22]). This results in specific behavior of the cuprates, which is unconventional from the viewpoint of "classical" superconductivity [32,[70][71][72][73].…”

Section: Results and Discussion A Fluctuation Conductivitymentioning

confidence: 99%

“…In accordance with the theory, in this temperature range the stiffness of the order parameter wave function of the superconducting Cooper pairs has to be maintained. As a result, in a definite temperature interval up to T 01 , the LPs behave like the SC Cooper pairs, which is a specific unusual property of HTSCs [22,32,70,71].…”

Section: B Pseudogap Analysismentioning

confidence: 99%

“…Thus, one may conclude that all high-T c superconductors behave in the same way at the approach to the T c from above. There is always the noticeable range of SC fluctuations just above T c [22,32,71] in which LPs behave like incoherent Cooper pairs, and excess conductivity is described by the AL [67] and HL [64] fluctuation theories.…”

Section: B Pseudogap Analysismentioning

confidence: 99%

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Specific temperature dependence of pseudogap in YBa2Cu3O7−δ nanolayers

et al. 2016

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The pseudogap (PG) derived from the analysis of the excess conductivity σ ′ (T ) in superlattices and double-layer films of YBa2Cu3O 7−δ − PrBa2Cu3O 7−δ (YBCO-PrBCO), prepared by pulsed laser deposition, is studied for the first time. The σ ′ (T ) analysis has been performed within the local-pair (LP) model based on the assumption of the paired fermion (LPs) formation in the cuprate highTc superconductors (cuprates) below the representative temperature T * ≫ Tc resulting in the PG opening. Within the model, the temperature dependencies of the PG, ∆ * (T ), for the samples with different number of the PrBCO layers (NP r ) were analyzed in the whole temperature range from T * down to Tc. Near Tc, σ ′ (T ) was found to be perfectly described by the Aslamasov-Larkin (AL) and Hikami-Larkin (HL) [Maki-Thompson (MT) term] fluctuation theories, suggesting the presence of superconducting fluctuations in a relatively large (up to 15 K) temperature range above Tc. All sample parameters were found to change with increase of NP r , finally resulting in the appearance of the pronounced maximum of ∆ * (T ) at high temperatures. The result is most likely due to increasing influence of the intrinsic magnetism of PrBCO (µP r ≈ 4 µB) and suggests the possibility to search in that way the change of interplay between the superconductivity and magnetism in cuprates.

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Section: Results and Discussion A Fluctuation Conductivitymentioning

confidence: 99%

Section: B Pseudogap Analysismentioning

confidence: 99%

Section: B Pseudogap Analysismentioning

confidence: 99%

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Specific temperature dependence of pseudogap in YBa2Cu3O7−δ nanolayers

et al. 2016

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“…It is also important to study whether a pseudogap and other orders coexist or are mutually exclusive. 15,[28][29][30] In this context, we study a symmetry-breaking state-a staggered flux (SF) state (sometimes called a d-density wave state)-as a possible pseudogap state for the Hubbard model. We should understand such a state in the context of a doped Mott insulator.…”

Section: Introductionmentioning

confidence: 99%

Staggered Flux State in Two-Dimensional Hubbard Models

2016

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The stability and other properties of a staggered flux (SF) state or a correlated d-density wave state are studied for the Hubbard (t-t ′ -U) model on extended square lattices, as a low-lying state that competes with the d x 2 −y 2 -wave superconductivity (d-SC) and possibly causes the pseudogap phenomena in underdoped high-T c cuprates and organic κ-BEDT-TTF salts. In calculations, a variational Monte Carlo method is used. In the trial wave function, a configurationdependent phase factor, which is vital to treat a current-carrying state for a large U/t, is introduced in addition to ordinary correlation factors. Varying U/t, t ′ /t, and the doping rate (δ) systematically, we show that the SF state becomes more stable than the normal state (projected Fermi sea) for a strongly correlated (U/t 5) and underdoped (δ 0.16) area. The decrease in energy is sizable, particularly in the area where Mott physics prevails and the circular current (order parameter) is strongly suppressed. These features are consistent with those for the t-J model. The effect of the frustration t ′ /t plays a crucial role in preserving charge homogeneity and appropriately describing the behavior of holeand electron-doped cuprates and κ-BEDT-TTF salts. We argue that the SF state does not coexist with d-SC and is not a 'normal state' from which d-SC arises. We also show that a spin current (flux or nematic) state is never stabilized in the same regime.

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“…According to the theory, the wave function phase stiffness has to be maintained up to T 01 [13,14]. This means that the superfluid density, n s , maintains a nonzero value up to T 01 [13,[28][29][30]. However, the details of the BEC-BCS transition are not fully clear so far as well [2,20,21,26,31].…”

Section: Introductionmentioning

confidence: 99%

Hydrostatic-pressure effects on the pseudogap in slightly doped YBa2Cu3O7−δ single crystals

Solovjov

Omelchenko

Вовк

et al. 2016

Physica B: Condensed Matter

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The influence of hydrostatic pressure up to P=1.05 GPa on resistivity, excess conductivity σ ′ (T ) and pseudogap ∆ * (T ) is investigated in slightly doped single crystals of Y Ba2Cu3O 7−δ (Tc(P = 0) ≈49.2 K and δ ≈ 0.5). The critical temperature Tc is found to increase with increasing pressure at a rate dTc/dP = +5.1 KGP a −1 , while ρ(300) K decreases at a rate dlnρ/dP = (−19±0.2)% GP a −1 . Near Tc, independently on pressure, the σ ′ (T ) is well described by the Aslamasov-Larkin and HikamiLarkin fluctuation theories, demonstrating a 3D-2D crossover with increase of temperature. The crossover temperature T0 determines the coherence length along the c-axis ξc(0) ≃ (3.43 ± 0.01)Å at P=0, which is found to decrease with increasing P. At the same time, ∆ * and the BCS ratio 2∆ * /kB Tc both increase with increasing hydrostatic pressure at a rate dln∆ * /dP ≈ 0.36 GP a −1 , implying an increase of the coupling strength with increasing P. At low temperatures below Tpair, the shape of the ∆ * (T ) curve is found to be almost independent on pressure. At high temperatures, the shape of the ∆ * (T ) curve changes noticeably with increasing P, suggesting a strong influence of pressure on the lattice dynamics. This unusual behavior is observed for the first time.

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Coexistence of the superconducting energy gap and pseudogap above and below the transition temperature of cuprate superconductors

Cited by 34 publications

References 26 publications

Specific temperature dependence of pseudogap in YBa2Cu3O7−δ nanolayers

Specific temperature dependence of pseudogap in YBa2Cu3O7−δ nanolayers

Staggered Flux State in Two-Dimensional Hubbard Models

Hydrostatic-pressure effects on the pseudogap in slightly doped YBa2Cu3O7−δ single crystals

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