<i>c</i>-axis response of single- and double-layered cuprates

Basov, D. N.; Mook, H. A.; Dąbrowski, B.; Timusk, T.

doi:10.1103/physrevb.52.r13141

Cited by 86 publications

(84 citation statements)

References 5 publications

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“…The optical conductivity σ 1 (ω) = ωǫ 2 (ω)/4π is shown in Fig.1(c). Notably, above 1000 cm −1 it is significantly smaller than the previously published values based solely on the KK analysis [13,14] (see inset in Fig.1(c)). The conductivity for selected frequencies is shown in Fig.2(a).…”

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confidence: 45%

c-Axis Optical Sum Rule and a Possible New Collective Mode inLa2−xS
Kuzmenko
¹
,
Tombros
²
,
Molegraaf
³

et al. 2003
Phys. Rev. Lett.
28
3
20
0
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We present the c-axis optical conductivity σ1c(ω, T ) of underdoped (x = 0.12) and optimally doped (x = 0.15) La2−xSrxCuO4 from 4 meV to 1.8 eV obtained by a combination of reflectivity and transmission spectra. In addition to the opening of the superconducting gap, we observe an increase of conductivity above the gap up to 270 meV with a maximal effect at about 120 meV. This may indicate a new collective mode at a surprisingly large energy scale. The Ferrell-Glover-Tinkham sum rule is violated for both doping levels. Although the relative value of the violation is much larger for the underdoped sample, the absolute increase of the low-frequency spectral weight, including that of the condensate, is higher in the optimally doped regime. Our results resemble in many respects the observations in YBa2Cu3O 7−δ .PACS numbers: 74.25. Gz, 78.20.Ci The charge transport between the CuO 2 planes in the high-T c cuprates forms one of the most intriguing puzzles of these materials. On the one hand the essential common physics seems to lie in the collective behavior of holes doped into a 2D Mott insulator, while the interplane conductivity strongly depends on the interlayer chemistry, which varies dramatically among different members of the high-T c family. On the other hand, it is the in-plane 'confinement' that preserves a possibility of significant lowering of the c-axis kinetic energy (KE) as the 3D coherent movement of the Cooper pairs is restored below T c [1,2], which, however, was shown to be a small effect in some single-layer compounds [3,4]. The models based on the KE lowering in the superconducting (SC) state predict the violation of the Ferrell-Glover-Tinkham (FGT) optical sum rule [5], which means that the spectral weight (SW) of the SC condensate is collected not only from energies of the order of 2∆ but also from higher frequencies. For the c-axis the violation has been experimentally tested in YBa 2 Cu 3 O 7−δ (YBCO) over a broad doping range and a significant increase of the relative violation value was found in the underdoped regime [6]. In the case of La 2−x Sr x CuO 4 (LSCO) a value of 50% has been reported for a slightly underdoped sample [7], although the doping dependence is still not known. Thus, the c-axis KE lowers in the SC state, which, however, leaves room for debate whether this is a by-product or the very reason for superconductivity [1,2,8,9].

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contrasting

confidence: 45%

c-Axis Optical Sum Rule and a Possible New Collective Mode inLa2−xS
Kuzmenko
¹
,
Tombros
²
,
Molegraaf
³

et al. 2003
Phys. Rev. Lett.
28
3
20
0
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“…On the other hand, transport measurements find a suppression of resistivity at a temperature T * , which is unusually high [81]. Infrared conductivity in the c-axis direction shows the presence of a pseudogap in the conductivity that starts near room temperature in slightly underdoped samples, but the overall suppression of conductivity is less complete than in the YBCO material [73,82,83].…”

Section: The Pseudogap and The Ab Plane Scattering Ratementioning

confidence: 96%

The mysterious pseudogap in high temperature superconductors: an infrared view

Timusk

2003

Solid State Communications

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We review the contribution of infrared spectroscopy to the study of the pseudogap in high temperature superconductors. The pseudogap appears as a depression of the frequency dependent conductivity in the c-axis direction and seems to be related to a real gap in the density of states. It can also be seen in the Knight shift, photoemission and tunneling experiments. In underdoped samples it appears near room temperature and does not close with temperature. Another related phenomenon that has been studied by infrared is the depression in the ab-plane scattering rate. Two separate effects can be discerned. At high temperatures there is broad depression of scattering below 1000 cm −1 which may be related to the gap in the density of states. At a lower temperature a sharper structure is seen, which appears to be associated with scattering from a mode at 300 cm −1 , and which governs the carrier life time at low temperatures. This mode shows up in a number of other experiments, as a kink in ARPES dispersion, and a resonance at 41 meV in magnetic neutron scattering. Since the infrared technique can be used on a wide range of samples it has provided evidence that the scattering mode is present in all high temperature cuprates and that its frequency in optimally doped materials scales with the superconducting transition temperature. The lanthanum and neodymium based cuprates do not follow this scaling and appear to have depressed transition temperatures.

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“…A characteristic pseudogap energy is easily identified from this data, but, again, it is not clear to us to what extent it is possible to identify a clear pseudogap temperature from this data. A pseudogap can also be deduced directly [143,144] from an analysis of σ ′ c (ω), where it manifests itself as a suppressed response at low frequencies, as shown in Fig. 9.…”

Section: What Does the Pseudogap Mean?mentioning

confidence: 99%

Concepts in High Temperature Superconductivity

Carlson

Kivelson

Orgad

et al. 2004

The Physics of Superconductors

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PrefaceIt is the purpose of this paper to explore the theory of high temperature superconductivity. Much of the motivation for this comes from the study of cuprate high temperature superconductors. However, we do not focus in great detail on the remarkable and exciting physics that has been discovered in these materials. Rather, we focus on the core theoretical issues associated with the mechanism of high temperature superconductivity. Although our discussions of theoretical issues in a strongly correlated superconductor are intended to be self contained and pedagogically complete, our discussions of experiments in the cuprates are, unfortunately, considerably more truncated and impressionistic.Our primary focus is on physics at intermediate temperature scales of order T c (as well as the somewhat larger "pseudogap" temperature) and energies of order the gap maximum, ∆ 0 . Consequently (and reluctantly) we have omitted any detailed discussion of a number of fascinating topics in cuprate superconductivity, including the low energy physics associated with nodal quasiparticles, the properties of the vortex matter which results from the application of a magnetic field, the effects of disorder, and a host of material specific issues. This paper is long enough as it is!

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c-axis response of single- and double-layered cuprates

Cited by 86 publications

References 5 publications

c-Axis Optical Sum Rule and a Possible New Collective Mode inLa2−xS
Kuzmenko
¹
,
Tombros
²
,
Molegraaf
³

et al. 2003
Phys. Rev. Lett.
28
3
20
0
View full text Add to dashboard Cite

c-Axis Optical Sum Rule and a Possible New Collective Mode inLa2−xS
Kuzmenko
¹
,
Tombros
²
,
Molegraaf
³

et al. 2003
Phys. Rev. Lett.
28
3
20
0
View full text Add to dashboard Cite

The mysterious pseudogap in high temperature superconductors: an infrared view

Concepts in High Temperature Superconductivity

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c-axis response of single- and double-layered cuprates

Cited by 86 publications

References 5 publications

c-Axis Optical Sum Rule and a Possible New Collective Mode inLa2−xSKuzmenko1, Tombros2, Molegraaf3 et al. 2003Phys. Rev. Lett.283200View full textAdd to dashboardCite

c-Axis Optical Sum Rule and a Possible New Collective Mode inLa2−xSKuzmenko1, Tombros2, Molegraaf3 et al. 2003Phys. Rev. Lett.283200View full textAdd to dashboardCite

The mysterious pseudogap in high temperature superconductors: an infrared view

Concepts in High Temperature Superconductivity

Contact Info

Product

Resources

About

c-Axis Optical Sum Rule and a Possible New Collective Mode inLa2−xS
Kuzmenko
¹
,
Tombros
²
,
Molegraaf
³

et al. 2003
Phys. Rev. Lett.
28
3
20
0
View full text Add to dashboard Cite

c-Axis Optical Sum Rule and a Possible New Collective Mode inLa2−xS
Kuzmenko
¹
,
Tombros
²
,
Molegraaf
³

et al. 2003
Phys. Rev. Lett.
28
3
20
0
View full text Add to dashboard Cite