Commensurate Spin Dynamics in the Superconducting State of an Electron-Doped Cuprate Superconductor

Yamada, Kōsaku; Kurahashi, Kazuyoshi; Uefuji, T.; Fujita, M.; Park, S; Lee, S H; Endoh, Y.

doi:10.1103/physrevlett.90.137004

Cited by 137 publications

(121 citation statements)

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“…The crystals exhibit the superconducting transition at 25 K and samples obtained with this method were already used in many studies [28,29]. Inelastic neutron scattering experiments were performed on the 1T spectrometer at the Orphée reactor using Cu(111) and Cu(220) monochromators and a pyrolithic graphite (002) analyzer.…”

Section: Methodsmentioning

confidence: 99%

Dispersion of the high-energy phonon modes inNd1.85Ce0.15CuO4

et al. 2005

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The dispersion of the high-energy phonon modes in the electron doped high-temperature superconductor Nd1.85Ce0.15CuO4 has been studied by inelastic neutron scattering. The frequencies of phonon modes with Cu-O bond-stretching character drop abruptly when going from the Brillouin zone center along the [100]-direction; this dispersion is qualitatively similar to observations in the hole-doped cuprates. We also find a softening of the bond-stretching modes along the [110]-direction but which is weaker and exhibits a sinusoidal dispersion. The phonon anomalies are discussed in comparison to hole-doped cuprate superconductors and other metallic perovskites.

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Section: Methodsmentioning

confidence: 99%

Dispersion of the high-energy phonon modes inNd1.85Ce0.15CuO4

et al. 2005

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“…However, AFLRO survives until superconductivity appears over a narrow range of δ, around the optimal doping δ ∼ 0.15 in the electrondoped cuprates 3,8,9 . In particular, the maximum achievable SC transition temperature in the electron-doped cuprates is much lower than that in the hole-doped case, and the commensurate spin response in the SC-state is observed 10 . These experimental observations show that the unconventional physical properties of both holedoped and electron-doped cuprates mainly depend on the extent of the doping concentration.…”

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Asymmetry of the electron spectrum in hole-doped and electron-doped cuprates

Guo

Feng

2006

Physics Letters A

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Within the t-t ′ -J model, the asymmetry of the electron spectrum and quasiparticle dispersion in hole-doped and electron-doped cuprates is discussed. It is shown that the quasiparticle dispersions of both hole-doped and electron-doped cuprates exhibit the flat band around the (π, 0) point below the Fermi energy. The lowest energy states are located at the (π/2, π/2) point for the hole doping, while they appear at the (π, 0) point in the electron-doped case due to the electron-hole asymmetry. Our results also show that the unusual behavior of the electron spectrum and quasiparticle dispersion is intriguingly related to the strong coupling between the electron quasiparticles and collective magnetic excitations. 74.25.Jb, 74.62.Dh, The parent compounds of cuprate superconductors are believed to belong to a class of materials known as Mott insulators with an antiferromagnetic (AF) longrange order (AFLRO), then superconductivity emerges when charge carriers, holes or electrons, are doped into these Mott insulators 1-3 . Although both hole-doped and electron-doped cuprates have the layered structure of the square lattice of the CuO 2 plane separated by insulating layers 1-3 , the significantly difference of the electronic states between hole-doped and electron-doped cuprates is observed 4,5 , which reflects the electron-hole asymmetry. For the hole-doped cuprates, AFLRO is reduced dramatically with doping 1,6 , and vanished around the doping δ ∼ 0.05. But a series of inelastic neutron scattering measurements show that the incommensurate short AF correlation persists in the underdoped, optimally doped, and overdoped regimes 1,6 , then in low temperatures, the systems become superconducting (SC) over a wide range of the hole doping concentration δ, around the optimal doping δ ∼ 0.15 2,7 . However, AFLRO survives until superconductivity appears over a narrow range of δ, around the optimal doping δ ∼ 0.15 in the electrondoped cuprates 3,8,9 . In particular, the maximum achievable SC transition temperature in the electron-doped cuprates is much lower than that in the hole-doped case, and the commensurate spin response in the SC-state is observed 10 . These experimental observations show that the unconventional physical properties of both holedoped and electron-doped cuprates mainly depend on the extent of the doping concentration. Since many of the unconventional physical properties, including the relatively high SC transition temperature, have often been attributed to particular characteristics of low energy excitations determined by the electronic structure 1,4 , then a central issue to clarify the nature of the unconventional physical properties is how the electronic structure evolves with the doping concentration, From the angle-resolved photoemission spectroscopy (ARPES) measurements 4,11 , it has been shown that the electron spectral function A(k, ω) in doped cuprates is strongly momentum and doping dependent. For the hole doping, the charge carriers doped into the parent Mott insulators first enter into the k = [π/...

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“…1a) 23,24 . PLCCO is a single-layer electron-doped copper oxide and was chosen to avoid the static AF order that coexists with superconductivity in Nd 1.85 Ce 0.15 CuO 4 (NCCO) 25 ; the T c = 24 K PLCCO is phase pure without static AF order 23,26 . Our elastic Q-scans through the expected AF Bragg positions confirm no static AF order to at least 600 mK in our PLCCO samples (Figs.…”

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Resonance in the electron-doped high-transition-temperature superconductor Pr0.88LaCe0.12CuO4-δ

Wilson

Dai

et al. 2006

Nature

131

184

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In conventional superconductors, the interaction that pairs the electrons to form the superconducting state is mediated by lattice vibrations (phonons) 1 . In hightransition temperature (high-T c ) copper oxides, it is generally believed that magnetic excitations play a fundamental role in the superconducting mechanism because superconductivity occurs when mobile 'electrons' or 'holes' are doped into the antiferromagnetic parent compounds 2 . Indeed, a sharp magnetic excitation termed "resonance" has been observed by neutron scattering in a number of hole-doped materials 3-11 . The resonance is intimately related to superconductivity 12 , and its interaction with charged quasi-particles observed by photoemission 13,14 , optical conductivity 15 , and tunneling 16 suggests that it plays a similar role as phonons in conventional superconductors. However, the relevance of the resonance to high-T c superconductivity has been in doubt because so far it has been found only in holedoped materials 17 . Here we report the discovery of the resonance in electron-doped superconducting Pr 0.88 LaCe 0.12 CuO 4-δ (T c = 24 K). We find that the resonance energy (E r ) is proportional to T c via E r = 5.8k B T c (k B is the Boltzmann's constant) for all high-T c superconductors irrespective of electron-or hole-doping (Fig. 1e). Our results demonstrate that the resonance is a fundamental property of the superconducting copper oxides and therefore must play an essential role in the mechanism of superconductivity.Although the interaction of electrons with phonons or magnetic excitations can cause electron pairing and superconductivity, we focus on magnetic excitations because the resonance is intimated related to superconductivity and also present in several classes of hole-doped high-T c materials. The resonance is a sharp magnetic excitation centered at the wavevector Q = (1/2, 1/2) in the two-dimensional reciprocal space of the CuO 2 planes, which corresponds to the antiferromagnetic (AF) Bragg position of the undoped compounds (Fig. 1a). It was first discovered in the hole-doped bilayer (each lattice unit cell has two CuO 2 planes) high-T c superconductor YBa 2 Cu 3 O 6+x (YBCO) 3 . Its intensity grows below T c and its energy ( ω) scales approximately with k B T c (Fig. 1e) We first probe the low-energy magnetic excitations of PLCCO using the SPINS cold neutron triple-axis spectrometer. The magnetic excitations are commensurate and The energy scans at Q = (1/2, 1/2, 0) confirm that the magnetic scattering between 0.5 meV and 4.5 meV is virtually temperature independent between 2 K and 30 K ( 2), the integrated intensity above background around (1/2, 1/2, 0) at ω = 8 and 10 meV shows a significant enhancement on cooling from 30 K to 2 K, but hardly changes on warming from 30 K to 80 K (Fig. 4d). The Q-width of the peak at ω = 10 meV is temperature independent and resolution-limited, giving a minimum ξ 45 ± 5 Å ( Fig. 3c). Similar scans using better collimations on BT-9 ( Figure 4a shows the energy dependence of the scattering...

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Commensurate Spin Dynamics in the Superconducting State of an Electron-Doped Cuprate Superconductor

Cited by 137 publications

References 29 publications

Dispersion of the high-energy phonon modes inNd1.85Ce0.15CuO4

Dispersion of the high-energy phonon modes inNd1.85Ce0.15CuO4

Asymmetry of the electron spectrum in hole-doped and electron-doped cuprates

Resonance in the electron-doped high-transition-temperature superconductor Pr0.88LaCe0.12CuO4-δ

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