Magnetic Field Dependence of the Superconducting Gap and the Pseudogap in Bi2212 and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>HgBr</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>-Bi2212, Studied by Intrinsic Tunneling Spectroscopy

Krasnov, Vladimir M.; Kovalev, A.E.; Yurgens, A.; Winkler, Dag

doi:10.1103/physrevlett.86.2657

Cited by 145 publications

(115 citation statements)

References 27 publications

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“…Several authors looked for the mechanism of superconductivity in the interplay between the electron correlation and el-ph interaction 74,75,72 . Here it should be noted that the recent tunneling experiments give evidence that the pseudo-gap and superconducting gap may be distinct [76][77][78] , while the low energy part of these gaps seems to be identical. If these picture is correct, which is still an open question 79 , this pseudo-gap play an essential roles in the physics of underdoped and optimally doped cuprates, which can not be captured by the perturbative analysis.…”

Section: Reducedmentioning

confidence: 99%

Role of the electron-phonon interaction in the strongly correlated cuprate superconductors

Shen

Lanzara

Ishihara

et al. 2002

Philosophical Magazine B

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Using high resolution angle-resolved photoemission data in conjunction with that from neutron and other probes, we show that electron-phonon (el-ph) coupling is strong in cuprates superconductors and it plays an important role in pairing. In addition to the strong electron correlation, the inclusion of phonons provides a theoretical framework explaining many important phenomena that cannot be understood by a strongly correlated electronic model alone. Especially it is indispensable to explain the difference among materials. The phonons with the wave number around the (0, qx) and (qx, 0) axes create the d-wave pairing while that near (π, π) are pair breaking. Therefore the half-breathing mode of the oxygen motions helps d-wave superconductivity.PACS numbers: 79.60. Bm, 73.20.Dx, It has been a long-standing question whether a strongly correlated electronic model of the CuO 2 plane, such as the t-J or Hubbard model alone, can explain the essential experimental observation of superconductivity in cuprates oxides. On the one hand, such a model has been remarkably successful in explaining many important physical properties, most notably the property of the undoped insulator and the renormalization of charge dynamics in it, by spin dynamics from t to J scale 1,2 and in predicting a spin gap 3-5 . On the other hand, important questions have been raised. The first is the observation that, while the CuO 2 plane conductivity is essentially the same for various families of cuprates, their T c vary by at least an order of magnitude 6,7 . The second is the observation that the phonons and lattice effects are clearly present in these materials 8 , following the original assumption that the Jahn-Teller (JT) polarons might be important for superconductivity 9 . There is currently no consensus on the above issues.Within the context of cuprates superconductors, it is difficult to understand some of the material specific properties by considering only the electronic degree of freedom. Fig. 1a summarizes the systematic in the superconducting gap size (∆), together with the transition temperature (T c ) shown in Fig. 1c. Unlike T c , which can be depressed by phase fluctuations in the underdoped regime 10-12 , the superconducting gap essentially reflects the pairing strength. It can be clearly seen that the pairing strength for the p-type cuprates is very strong, with gap sizes that are at least an order of magnitude larger than conventional superconductors. Further, the maximum T c of each family is controlled by the maximum superconducting gap size. This is most dramatically illustrated by the HgBa 2 Ca n−1 Cu n O 2(n+1) (Hg1223 for n=3) compound, which has a much larger gap size as well as T c . Fig 1a also clearly shows a discrepancy between pand n-type materials, as superconductivity in a n-type material appears to be very fragile with a much weaker pairing strength. The electron-hole asymmetry is particularly perplexing in the context of spin pairing only, as magnetism is very strong and persists to a much wider range in the n-...

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Section: Reducedmentioning

confidence: 99%

Role of the electron-phonon interaction in the strongly correlated cuprate superconductors

Shen

Lanzara

Ishihara

et al. 2002

Philosophical Magazine B

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“…Indeed, an interlayer spacing of 15.5Å was estimated from a periodic Fraunhofer modulation of Fiske steps in Bi-2212 mesas [2]. At present, high quality SIStype IJJ's can be fabricated using HTSC mesa structures [3,4]. IJJ's with their record large I c R n values ∼ 10mV are attractive candidates for cryoelectronics.…”

Section: Introductionmentioning

confidence: 99%

Stacked Josephson junction SQUID

Krasnov¹

2002

Physica C: Superconductivity

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Operation of a Superconducting Quantum Interference Device (SQUID) made of stacked Josephson junctions is analyzed numerically for a variety of junction parameters. Due to a magnetic coupling of junctions in the stack, such a SQUID has certain advantages as compared to an uncoupled multi-junction SQUID. Namely, metastability of current-flux modulation can be reduced and a voltage-flux modulation can be improved if junctions in the stack are phase-locked. Optimum operation of the SQUID is expected for moderately long, strongly coupled stacked Josephson junctions. A possibility of making a stacked Josephson junction SQUID based on intrinsic Josephson junctions in high-Tc superconductor is discussed.

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“…Turning to the pseudogap, specific heat [8] and tunneling measurements [21] show that the pseudogap is nonstates-conserving, with an approximately triangular energy dependence, and pinned to the Fermi level, E F . We assume therefore a triangular normal-state DOS: …”

mentioning

confidence: 99%

Isotope Effect in the Superfluid Density of High-Temperature Superconducting Cuprates: Stripes, Pseudogap, and Impurities

et al. 2005

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Underdoped cuprates exhibit a normal-state pseudogap, and their spins and doped carriers tend to spatially separate into 1-or 2-D stripes. Some view these as central to superconductivity, others as peripheral and merely competing. Using La2−xSrxCu1−yZnyO4 we show that an oxygen isotope effect in Tc and in the superfluid density can be used to distinguish between the roles of stripes and pseudogap and also to detect the presence of impurity scattering. We conclude that stripes and pseudogap are distinct, and both compete and coexist with superconductivity.PACS numbers: 71.10. Hf, 74.25.Dw, 74.62.Dh, 74.72.Dn High-T c superconductors (HTS) remain a puzzle. Various correlated states have been identified in HTS including antiferromagnetism, the pseudogap[1], nanoscale spin-charge stripes [2] and, of course, superconductivity (SC). (Here we generalise"stripes" to include possible 2D checkerboard structures [3]). The pseudogap is a nodal energy gap of uncertain origin that appears in the normal-state (NS) density of states (DOS). Its effects can be observed in many physical properties [1,4]. Several opposing views are still current. One is that stripes play a central role [5], forming the pseudogap correlation [6] and/or mediating the SC pairing. Another is that the NS pseudogap arises from incoherent superconducting fluctuations which set in well above T c [7]. Another is that these states are independently competing [8]. Here stripes and pseudogap play a secondary role and SC is mediated by some other pairing boson. An unambiguous test of these opposing views is urgently needed. We show here that isotope effects provide such a test.The isotope exponent α(E) in a given property E is defined as α(E) = − (∆E/E)/(∆M/M ), where M is the isotopic mass and E may be T c , the SC gap parameter, ∆ 0 , the pseudogap energy scale, E g , or the superfluid density ρ s = λ −2 ab = µ 0 e 2 (n s /m * ab ). (λ ab is the in-plane London penetration depth, n s is the carrier density and m * ab is the effective electronic mass for in-plane transport). An isotope effect on T c was first discovered in 1950 by Allen et al. for Sn [9]. They found α(T c ) ≈ 0.5 ± 0.05 which provided the central clue for the role of phonons in pairing and led 7 years later to the BCS theory of SC [10].The situation with HTS is more complex. The oxygen isotope effect on T c was found[11] to be small, with α(T c ) ≈ 0.06. However, with decreasing doping the effect rises and eventually diverges as T c → 0[12, 13]. Surprisingly, an isotope effect was also found in the superfluid density [14] (and attempts were made to resolve this into a dominant isotope effect just in m * [15,16]). We will show that both of these unusual effects can be understood in terms of a normal-state pseudogap which competes with SC [17]. We also predict and confirm an isotope effect in ρ s induced by impurity scattering. The isotope effects in T c and ρ s are mapped as a function of doping in La 2−x Sr x Cu 1−y Zn y O 4 and we observe a canonical pseudogap behavior as well as a huge an...

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Magnetic Field Dependence of the Superconducting Gap and the Pseudogap in Bi2212 andHgBr2-Bi2212, Studied by Intrinsic Tunneling Spectroscopy

Cited by 145 publications

References 27 publications

Role of the electron-phonon interaction in the strongly correlated cuprate superconductors

Role of the electron-phonon interaction in the strongly correlated cuprate superconductors

Stacked Josephson junction SQUID

Isotope Effect in the Superfluid Density of High-Temperature Superconducting Cuprates: Stripes, Pseudogap, and Impurities

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