Fiory<i>et al</i>. reply

Fiory, A. T.; Af, Hebard; Eick, R. H.; Pm, Mankiewich; Howard, R. E.; Ml, O'Malley

doi:10.1103/physrevlett.67.3196

Cited by 28 publications

(30 citation statements)

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“…More recent results using direct magnetic measurements on epitaxial YBaCuO films by Fiory et al 30 and on bulk crystal platelets by Krusin-Elbaum et al have also shown a weak lowtemperature dependence. At higher temperature, the results fitted either the strong or weak-coupling singlet BCS forms.…”

Section: A(t) CC A(0)[1 -(T/t C ) 4 F 1/2 (32)mentioning

confidence: 81%

“…They found that the temperature dependence of the zero-field-cooled dM/dln(t) showed a peak around 30 flux penetration was detected at far lower fields. This suggests that the direct magnetic measurement is sensitive to grain-boundary flux penetration, while the vibrating read detects the bulk penetration and thus can be used to measure the bulk H cl .…”

Section: Perhaps the Large Relaxation In Ceramics Was Not Surprising mentioning

confidence: 96%

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Macroscopic Magnetic Properties of High Temperature Superconductors

Malozemoff

1998

Physical Properties of High Temperature Superconductors I

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Section: A(t) CC A(0)[1 -(T/t C ) 4 F 1/2 (32)mentioning

confidence: 81%

Section: Perhaps the Large Relaxation In Ceramics Was Not Surprising mentioning

confidence: 96%

Macroscopic Magnetic Properties of High Temperature Superconductors

Malozemoff

1998

Physical Properties of High Temperature Superconductors I

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“…At 10 K, we obtain ^ = 1600 A, in excellent agreement with independent penetrationdepth measurements on YBa2Cu 3 C>7 single crystals and films. 15, 16 The good fit of the l/co curve to the data at 10 K also shows that the penetration depth is not dependent on frequency at this temperature. Figure 2 plots the absorptive part o\ of the conductivity.…”

mentioning

confidence: 83%

Dynamic conductivity and coherence peak inYBa2Cu3
Nuss
¹
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Mankiewich
²
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O'Malley
³

et al. 1991
Phys. Rev. Lett.
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We measure directly both the real and imaginary parts of the sub-band-gap conductivity a in YBa2Cu3<>7 in the 15-80 cm -1 frequency range using coherent time-domain terahertz spectroscopy. We observe a peak in the real part o\ similar to the coherence peak expected in an s-wave BCS superconductor. The absence of such a peak in NMR relaxation-rate experiments suggests that its origin lies in a strongly temperature-dependent inelastic-scattering rate rather than in coherence factors.PACS numbers: 74.30. Gn, 74.70.Vy, 84.40.Cb Measurements of the dynamic response of conventional superconductors have played a crucial role in understanding the origin of superconductivity and in establishing the microscopic Bardeen-Cooper-Schrieffer x (BCS) theory of superconductivity. For instance, far-infrared transmission and reflectivity measurements provided the existence proof for the superconducting energy gap in lead 2 and indications for strong-coupling effects in NbN films. 3 In the high-temperature superconductors, reflectivity measurements on YBa2Cu3C>7 single crystals and films 4 " 6 as well as transmission measurements on Bi2Sr2CaCu20g cleaved crystals 7 have been performed, but unfortunately with widely diverging results and interpretations.In this Letter, we present measurements of both the real and imaginary parts of the conductivity a of highquality superconducting YBa2Cu3C>7 films in the frequency range from 500 GHz to 2.5 THz (15-80 cm -1 ) by coherent time-domain terahertz spectroscopy. Unlike conventional Fourier-transform far-infrared spectroscopy, owing to its phase sensitivity, this technique permits us to measure both the real and imaginary parts of the conductivity simultaneously without referring to the Kramers-Kronig relations. Furthermore, we can study thin superconducting films in transmission, which offers greatly increased accuracy compared to reflection measurements, where the reflectivity is close to unity for energies below the gap.This novel spectroscopic technique has recently been successfully applied to the measurement of the conductivity of doped semiconductors, 8 the absorption coefficient and refractive index of dielectrics, 9 the measurement of the superconducting band gap in niobium films, 10 as well as the surface impedance of YBa2Cu3C>7 superconducting films. 11 The setup of our coherent time-domain spectrometer is similar to the one described earlier, 10,11 but includes additional focusing optics for small samples. It resembles a conventional spectrometer, but here the electromagnetic far-infrared radiation is generated and detected by time-resolved optoelectronic techniques, which results in the phase sensitivity of the technique. Both source and detector consist of 50-/im dipole antennas with integrated radiation-damaged silicon-on-sapphire photoconductive switches. 12 The transmitter antenna, which is biased with a dc voltage, emits a short electromagnetic burst with a broad frequency spectrum extending from almost dc to more than 2.5 THz when the 100-fs optical pulse from a colli...

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“…Some of the experiments are consistent with conventional BCS theory which has a superconducting gap over the entire Fermi surface, while other experiments suggest an unconventional pairing mechanism in which the gap is zero on portions of the Fermi surface. In addition, there are two recent measurements of X(T) in oaxis-oriented but polycrystalline films 14,15 which also give conflicting results. The probable cause of such significant disagreement among prior measurements is the polycrystalline nature of the samples.…”

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confidence: 99%