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Hofer, J.; Conder, K.; Sasagawa, T.; Zhao, Guangyao; Willemin, M.; Keller, H.; Kishio, K.

doi:10.1103/physrevlett.84.4192

Cited by 105 publications

(161 citation statements)

References 21 publications

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“…9. It is clear that T c is lower for the 18 More interestingly, the inplane penetration depth λ ab (T ) can be extracted from field-dependent measurements [42]. Fig.…”

Section: Large Oxygen-isotope Effect On the Effective Supercarriementioning

confidence: 99%

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Unconventional isotope effects in the high-temperature cuprate superconductors

Zhao

Keller

Conder

2001

J. Phys.: Condens. Matter

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139

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We review various isotope effects in the high-Tc cuprate superconductors to assess the role of the electron-phonon interaction in the basic physics of these materials. Of particular interest are the unconventional isotope effects on the supercarrier mass, on the charge-stripe formation temperature, on the pseudogap formation temperature, on the EPR linewidth, on the spin-glass freezing temperature, and on the antiferromagnetic ordering temperature. The observed unconventional isotope effects strongly suggest that lattice vibrations play an important role in the microscopic pairing mechanism of high-temperature superconductivity.

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“…9. It is clear that T c is lower for the 18 More interestingly, the inplane penetration depth λ ab (T ) can be extracted from field-dependent measurements [42]. Fig.…”

Section: Large Oxygen-isotope Effect On the Effective Supercarriementioning

confidence: 99%

“…The superconducting transition was studied by cooling the sample in a magnetic field B a = 0.1 T applied at an angle of 45 • with respect to the c-axis [42]. The torque signal was continuously recorded upon cooling the sample at a cooling rate of 0.01 K/s.…”

Section: Large Oxygen-isotope Effect On the Effective Supercarriementioning

confidence: 99%

Unconventional isotope effects in the high-temperature cuprate superconductors

Zhao

Keller

Conder

2001

J. Phys.: Condens. Matter

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139

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“…These continue to track up the canonical curve, showing that the pseudogap and impurity scattering have essentially the same effect in such a plot. To this data we add previously-reported [26] values for La 2−x Sr x CuO 4 obtained using muon spin relaxation (µSR) with x = 0.080 and 0.086 (blue down triangles). The collective data is generally consistent with the model.…”

Section: Remain Unchangedmentioning

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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“…On the other hand, there is overwhelming evidence that electron-phonon coupling is very strong in the cuprate superconductors [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . In particular, various unconventional oxygen-isotope effects Zhao and his coworkers have observed since 1994 clearly indicate that the electron-phonon interactions are so strong that polarons/bipolarons are formed in doped cuprates [5][6][7][8][9]11,12,[14][15][16][17]19 and manganites 21,22 , in agreement with a theory of high-temperature superconductivity 23 and the original motivation for the discovery of high-temperature superconductivity 1 .…”

Section: Introductionmentioning

confidence: 99%

Pairing interactions and pairing mechanism in high-temperature copper oxide superconductors

Zhao

2005

Phys. Rev. B

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The polaron binding energy Ep in undoped parent cuprates has been determined to be about 1.0 eV from the unconventional oxygen-isotope effect on the antiferromagnetic ordering temperature. The deduced value of Ep is in quantitative agreement with that estimated from independent optical data and that estimated theoretically from the measured dielectric constants. The substantial oxygenisotope effect on the in-plane supercarrier mass observed in optimally doped cuprates suggests that polarons are bound into the Cooper pairs. We also identify the phonon modes that are strongly coupled to conduction electrons from the angle-resolved photoemission spectroscopy, tunneling spectra, and optical data. We consistently show that there is a very strong electron-phonon coupling feature at a phonon energy of about 20 meV along the antinodal direction and that this coupling becomes weaker towards the diagonal direction. We further show that high-temperature superconductivity in cuprates is caused by strong electron-phonon coupling, polaronic effect, and significant coupling with 2 eV Cu-O charge transfer fluctuation.

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Oxygen-Isotope Effect on the In-Plane Penetration Depth in UnderdopedLa2−xSrxCuO

Cited by 105 publications

References 21 publications

Unconventional isotope effects in the high-temperature cuprate superconductors

Unconventional isotope effects in the high-temperature cuprate superconductors

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

Pairing interactions and pairing mechanism in high-temperature copper oxide superconductors

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