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Demšar, Jure; Podobnik, B.; Kabanov, V. V.; Wolf, Th.; Mihailović, D.

doi:10.1103/physrevlett.82.4918

Cited by 291 publications

(303 citation statements)

References 18 publications

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“…As T c is approached from below, τ R shows a divergence [see inset to Fig. 2 b)] as observed already in YBCO, Tl-2223 [3,6] and also in NCCO [5]. This is, through the relation τ R ∝ 1/∆(T), associated with the closure of the isotropic collective mean-field-like gap [1].…”

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confidence: 95%

“…In YBCO two distinct relaxation components below T c (one present also above T c with T-independent τ, and the other with divergent τ R at T c [3,6]) suggest the co-existing presence of two distinct energy gaps: a T-independent pseudogap ∆ p and a mean-field-like T-dependent gap ∆ c (T) [3]. Two distinct relaxation components with opposite signs were observed also on BiSCO-2212 and Tl-2201 [4], suggesting that the two component behavior is quite general in high-T c superconductors near optimal doping.…”

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confidence: 99%

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Quasiparticle relaxation dynamics in Hg-1223 studied by femtosecond time-resolved optical spectroscopy.

Demšar¹,

Hudej²,

Karpiński³

et al. 2000

Physica C: Superconductivity

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Following recent progress in understanding the relaxation dynamics of photoexcited carriers in materials exhibiting a small gap in the low-energy excitation spectrum we have performed pump-probe measurements on near optimally doped Hg-1223. We show that the behavior is very similar as in optimally-doped YBCO, where the data can be interpreted with the coexisting presence of two energy gaps: normal state T-independent pseudogap and a mean-field-like collective gap, associated with intrinsic spatially inhomogeneous ground state. An important difference between the two compounds is found in the low temperature relaxation time, which in Hg-1223 is found to be strongly temperature dependent.In femtosecond pump-probe experiments, an ultrashort laser pump pulse first excites electron-hole pairs via an interband transition in the material. In a process, which is similar in most materials including metals, semiconductors and superconductors [1], these hot carriers very rapidly release their energy via e-e and e-ph collisions reaching states near the Fermi energy within 10 -100 fs. The superconducting gap inhibits further relaxation and photoexcited carriers accumulate above the gap [1]. The bottleneck causes a transient change in reflectivity ∆R/R, with the amplitude of the reflectivity transient being proportional to the photoexcited carrier density [1]. Because the final relaxation step across the gap is strongly suppressed, the quasiparticles (QP) together with high frequency phonons (with ω > 2∆) form a near-steady state distribution, with the QP recombination dynamics of this system being governed by the emission and reabsorption of high frequency phonons. As the gap closes (in case of T-dependent BCS-like gap), more and more high frequency phonons have the energy to excite Cooper pairs, therefore the relaxation time τ R is expected to show a divergence [1] as τ R

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confidence: 95%

mentioning

confidence: 99%

Quasiparticle relaxation dynamics in Hg-1223 studied by femtosecond time-resolved optical spectroscopy.

Demšar¹,

Hudej²,

Karpiński³

et al. 2000

Physica C: Superconductivity

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“…The term pseudogap has been coined to describe this kind of physics. The presence of pseudogap has been established through the measurements of the nuclear magnetic resonance (NMR) [5], the scanning tunneling spectroscopy [6][7][8][9], the analysis of the electronic Raman scattering [10][11][12], through time-resolved optical spectroscopy [13][14][15][16][17][18], and through the ARPES [19][20][21][22][23][24][25]. The observed strong Nernst effect in cuprates has been also attributed to it [26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Spin Polaron-Bipolaron Scenario of Three Gap-Like Energy Scales in Superconducting Cuprates

et al. 2010

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We argue that three gaps observed in underdoped cuprates can be attributed to the formation of antiferromagnetic spin polarons and bipolarons. Within the spin polaron scenario the antinodal pseudogap at he high energy scale originates from the change of the Fermi surface topology, induced by antiferromagnetic correlations. That change gives rise to the diminishing of the spectral weight at the antinodal region near the Brillouin zone boundary. We demonstrate that effect by analyzing effective models of doped antiferromagnets. The second type of pseudogap appearing at the intermediate energy scale originates from the phenomena which are precursory to superconductivity and predominantly concern the portion of the Fermi surface near the nodal region. In order to analyze the latter phenomenon we use the negative U Hubbard model, in which many details typical to spin polaron physics are neglected, but which contains the essential ingredient of it, that is the strong short range attraction. The lowest energy scale is related to the true superconducting gap which develops with doping, although both types of pseudogap diminish with doping. This behavior can be explained by the fact that the spin polaron band is empty in the undoped system and therefore the formation of the superconducting state in the system is forbidden. Due to a pedagogical character of this report, we present in the introduction a short overview of mostly recent experimental results which are related to the gap-pseudogap physics.

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“…Although the interaction of electrons with lattice vibrations is not likely to solely account for the essential properties of high-T c superconductors (HTSCs), many probes including angle-resolved photoemission, [1][2][3][4][5] inelastic neutron scattering, 6 , tunneling 7,8 and Raman 9 spectroscopies have revealed that electron-phonon interactions have significant effects on various properties. Complementary to the timeintegrated techniques, different ultrafast pump-probe techniques [10][11][12][13][14][15] have been used to disentangle microscopic interactions in HTSCs. These techniques aim to study the recombination of photoexcited quasiparticles and the resulting recovery of the superconducting condensate.…”

Section: Introductionmentioning

confidence: 99%

Theory of ultrafast quasiparticle dynamics in high-temperature superconductors: The dependence on pump fluence

et al. 2012

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We present a theory for the time-resolved optical spectroscopy of high-temperature superconductors at high excitation densities with strongly anisotropic electron-phonon coupling. A signature of the strong coupling between the out-of-plane, out-of-phase O buckling mode (B1g) and electronic states near the antinode is observed as a higher-energy peak in the time-resolved optical conductivity and Raman spectra, while no evidence of the strong coupling between the in-plane Cu-O breathing mode and nodal electronic states is observed. More interestingly, it is observed that under appropriate conditions of pump fluence, this signature exhibits a re-entrant behavior with time delay, following the fate of the superconducting condensate.

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Superconducting GapΔc, the PseudogapΔp, and

Cited by 291 publications

References 18 publications

Quasiparticle relaxation dynamics in Hg-1223 studied by femtosecond time-resolved optical spectroscopy.

Quasiparticle relaxation dynamics in Hg-1223 studied by femtosecond time-resolved optical spectroscopy.

Spin Polaron-Bipolaron Scenario of Three Gap-Like Energy Scales in Superconducting Cuprates

Theory of ultrafast quasiparticle dynamics in high-temperature superconductors: The dependence on pump fluence

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