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Mesot, J.; Norman, M. R.; Ding, Hong; Randeria, Mohit; Campuzano, J. C.; Paramekanti, Arun; Fretwell, H. M.; Kaminski, Adam; Takeuchi, Tsunehiro; Yokoya, Takayoshi; Sato, Takafumi; Takahashi, Toru; Mochiku, Takashi; Kadowaki, K.

doi:10.1023/a:1022569616840

Cited by 45 publications

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“…We think that the low temperature behavior of the penetration depth is interesting as a typical problem of the superconductivity in the strongly correlated electron systems. 68,66,67,69,70) In particular, the strongly anisotropic High-T c cuprates are expected to have the characteristic temperature and doping dependences. The Uemura plot is a typical one.…”

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confidence: 99%

“…66) Moreover, the inconsistency of the absolute value Λ(0) and the coefficient of the T-linear term of Λ(T ) has been pointed out on the analogy of the result for the isotropic system. 67,69,68) The absolute value Λ(0) decreases with under-doping, while the coefficient of the T-linear term is almost independent of the doping. 67) We consider that the inconsistency is understood by considering the momentum dependence of the current vertex J ν .…”

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confidence: 99%

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Theory on Superconducting Transition from Pseudogap State

2000

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The anomalous properties of High-T c cuprates are investigated both in the normal state and in the superconducting state. In particular, we pay attention to the pseudogap in the normal state and the phase transition from the pseudogap state to the superconducting state. The pseudogap phenomena observed in cuprates are naturally understood as a precursor of the strong coupling superconductivity. We have previously shown by using the self-consistent Tmatrix calculation that the pseudogap is a result of the strong superconducting fluctuations which are accompanied by the strong coupling superconductivity in quasi-two dimensional systems [J. Phys. Soc. Jpn. 68 (1999) 2999.]. We extend the scenario to the superconducting state. The close relation between the pseudogap state and the superconducting state is pointed out. Once the superconducting phase transition occurs, the superconducting order parameter rapidly grows rather than the result of BCS theory. With the rapid growth of the order parameter, the gap structure becomes sharp, while it is remarkably broad in the pseudogap state. The characteristic energy scale of the gap does not change. These results well explain the phase transition observed in the spectroscopic measurements. Further, we calculate the magnetic and transport properties which show the pseudogap phenomena. The comprehensive understanding of the NMR, the neutron scattering, the optical conductivity and the London penetration depth is obtained both in the pseudogap state and in the superconducting state. Many experiments such as the nuclear magnetic resonance (NMR), 1) optical conductivity, 2) transport, 3) electronic specific heat, 4) angle-resolved photo-emission spectroscopy (ARPES), 5) tunneling *

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Section: (B))mentioning

confidence: 99%

Theory on Superconducting Transition from Pseudogap State

2000

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“…The d-wave symmetry deviation in the underdoped region is connected with the existence of the high-harmonic pairing terms [27].…”

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Anisotropy of the gap parameter in the hole-doped cuprates

Szczȩśniak¹,

Durajski²

2014

Supercond. Sci. Technol.

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The structure of the gap parameter (∆ k ) for the hole-doped cuprates has been studied. The obtained results indicate that the antinodal part of ∆ k is very weakly temperature dependent and above the critical temperature (TC), it extends into the anomalous normal state to the pseudogap temperature. On the other hand, the values of ∆ k , which are close to the nodal part, are strongly temperature dependent. The model has been tested for the YBa2Cu3O 7−δ superconductor. It has been shown that the theoretical results agree with the experimental data.Keywords: High-temperature superconductors; Anisotropy; Energy gap. [20]. So far, the obtained results have been interpreted in the framework of the two different approaches.In the first case, the difference between the doping and temperature dependence of the gap in the nodal and antinodal region suggests that the pseudogap and the superconducting gap are independent [21], [22]. Additional support comes from the strong deviation from the standard d-wave form of the energy gap in the underdoped region. The above fact is interpreted as composition of the d-wave superconducting gap and the remnant pseudogap [23], [24].In the second case, the pseudogap is considered as the precursor of the superconducting gap [25], [26]. The d-wave symmetry deviation in the underdoped region is connected with the existence of the high-harmonic pairing terms [27].In the presented paper, we have studied the anisotropy of the gap parameter for the hole-doped superconductors in the framework of the recently introduced theory [28], [29].Our main purpose was to derivation the thermodynamic equation for the anomalous thermal average, which determines the structure of the gap parameter. Next, the temperature dependence of the nodal and the antinodal part of the energy gap has been calculated. We have assumed that the theory should be simple enough as far as possible. However, the good agreement between the theoretical predictions and the experimental results has been also required.The model is based on three postulates: (i) In the superconductivity domain of the cuprates the fundamental role is played by the electrons on the CuO 2 planes. (ii) The conventional electron-phonon (EPH) interaction exists in the cuprates, which does not have to be strong. (iii) Strong electronic correlations exist in the cuprates, but the electron-electron scattering in the superconductivity domain is inseparably connected with absorption or emission of the vibrational quanta.The first postulate emphasizes the importance of the quasi two-dimensionality of the system. The second one refers to the classical pairing mechanism given by Fröhlich [30], [31]. The third postulate states that the strong electron correlations in the cuprates are inseparably coupled with the phonon subsystem. The first two postulates define the van Hove scenario [32], [33]. The third postulate requires further discussion because it is far more subtle. In particular, it should be noted that the postulated electron correlations generalize the Hubb...

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“…T C0 is the meanfield transition temperature. 1/λ 2 (T ) and γ(T ) are determined from the usual FS integrals over k-space and energy.For simplicity, we neglect possible deviations of ∆(k, T ) from ∆ 0 (T )cos(2φ) which are reported in ARPES measurements on underdoped Bi 2 Sr 2 Ca 1 Cu 2 O 8+δ (BSCCO) [18] and which may or may not be present in YBCO. Pos-1…”

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“…For simplicity, we neglect possible deviations of ∆(k, T ) from ∆ 0 (T )cos(2φ) which are reported in ARPES measurements on underdoped Bi 2 Sr 2 Ca 1 Cu 2 O 8+δ (BSCCO) [18] and which may or may not be present in YBCO. Pos-sible anomalous behavior of the quasi-1D CuO chains [19] is not included.…”

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Effect of the pseudogap on the temperature dependence of the magnetic penetration depth in YBCO films

Boyce

Skinta

Lemberger

2000

Physica C: Superconductivity

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We report measurements of the ab-plane penetration depth, λ(T ), in YBa2Cu3O 7−δ films at various δ. At optimal doping, critical fluctuation effects are absent, and 1/λ 2 (T ) from 4 K to 0.99 TC is that of a clean, strong-coupling d-wave superconductor with ∆0(0)/kBTC ≃ 3.3. As in crystals, underdoping reduces the superfluid density, ns(0) ∝ 1/λ 2 (0), without affecting the low-T slope of 1/λ 2 (T ). These results, as well as electronic heat capacity data, are well described by an ad hoc model in which contributions to the superfluid and entropy are lost from regions of the Fermi surface occupied by the pseudogap.PACS Nos. 74.25.Fy, 74.25.Nf, 74.40.+k, 74.76.Bz A large body of experimental evidence indicates the opening of a k-dependent gap, or pseudogap, at a temperature, T * , above the superconducting transition temperature, T C , in underdoped cuprates [1]. The pseudogap competes with the superconducting gap: T * and the fraction of the Fermi surface (FS) occupied by the pseudogap increase with underdoping, while T C , the superfluid density in the ab-plane, n S (0), and the peak value of the electronic specific heat coefficient, γ(T ), at T C decrease. A great deal of effort currently focuses on understanding the coexistence of these two gaps. Lee and coworkers propose that the fundamental physics lies in spin-charge separation, a key element being the segmentation of the FS into regions either occupied or unoccupied by the pseudogap in the normal state [2]. With this in mind, we construct a simple model to describe our measurements of n S (T ) and literature results for γ(T ), in which only portions of the FS unoccupied by the pseudogap contribute to the superfluid and entropy in the superconducting state.We present new measurements of 1/λ 2 (T ) ∝ n S (T ) in YBa 2 Cu 3 O 7−δ (YBCO) films at various δ. We show that 1/λ 2 (T ) in optimally-doped films is that of a clean, strong-coupling d-wave superconductor with a full FS. Underdoped films are well described by a Fermi liquidlike model, in which electronic properties are expressed as integrals over the FS, but the integrals extend only over sections of the FS not occupied by the pseudogap in the normal state. The fraction of the FS that survives is equal to the ratio of n S (0) of the underdoped film to n S,opt. (0) of the same film at optimal doping.The absence of critical fluctuations in optimally-doped YBCO films [3] and measurements of the effect of thermal phase fluctuations on 2D films of a conventional superconductor [4] lead us to conclude that fluctuation effects are weak in the underdoped films. However, the relative importance of thermal phase fluctuations (TPF's) to single particle excitations is controversial. Carlson et al. [5] have shown numerically that a fluctuation driven superfluid density in Josephson junction (JJ) arrays displays features similar to some very clean YBCO crystals, namely, T -linear behavior at low-T [6], T C roughly proportional to n S (0), and a wide critical region [7,8]. Terahertz measurements of the sheet condu...

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Cited by 45 publications

References 3 publications

Theory on Superconducting Transition from Pseudogap State

Theory on Superconducting Transition from Pseudogap State

Anisotropy of the gap parameter in the hole-doped cuprates

Effect of the pseudogap on the temperature dependence of the magnetic penetration depth in YBCO films

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