Electronic inhomogeneity and competing phases in electron-doped superconducting<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Pr</mml:mi><mml:mn>0.88</mml:mn></mml:msub><mml:mi mathvariant="normal">La</mml:mi><mml:msub><mml:mi mathvariant="normal">Ce</mml:mi><mml:mn>0.12</mml:mn></mml:msub><mml:mi mathvariant="normal">Cu</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>4</mml:mn><mml:mo>−</mml:mo><mml:mi>δ

Dai, Pengcheng; Kang, Hye Jung; Mook, H. A.; Matsuura, Masato; Lynn, J. W.; Kurita, Y.; Komiya, Seiki; Ando, Yoichi

doi:10.1103/physrevb.71.100502

Cited by 38 publications

(68 citation statements)

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“…In the present model, the annealing process diminishes any Cu deficiency and therefore promotes the electron-doping effect of Ce, which also suppresses the AF Néel temperature (T N ). Our recent systematic neutron diffraction measurements on PLCCO as a function of annealing process showed that the T N of PLCCO drops from 186 K in an ag-NSC sample to <600 mK in an r-SC sample (T c = 24 K) 27,28 .From recent Hall coefficient measurements, Gauthier et al 29 argue that the annealing process does not affect the carrier concentration but rather affects the mobility of the carriers. Since random Cu and oxygen vacancies in the CuO 2 plane break the translational symmetry of the CuO 2 plane, they can act as impurity centers to localize the doped electrons.…”

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“…31) have recently determined the Fermi surface topology and the superconducting gap function in electron-doped materials. However, the quality of the sample surfaces studied has not been conclusively established, and one must now consider the possible effect of an exposed NSC R 2 O 3 surface in future ARPES and scanning tunneling microscopy experiments.Furthermore, it should also be possible to grow higher-quality single-crystal T' structured copper oxides by adding excess Cu in the starting materials to eliminate Cu deficiencies and subsequent R 2 O 3 contamination.Because of the availability of single crystals of the T' structured copper oxides, the vast majority of transport, structural, magnetic, and electronic-property measurements of electron-doped superconductors have been obtained from these materials [9][10][11][12][13][14][15][16][17][18][19][20][21][22]25,[27][28][29][30][31] . For other electron-doped high-T c superconductors with different crystal structure types, such as the infinite-layer Sr 1-x La x CuO 2 family 32-34 , the microscopic process of inducing superconductivity is still unclear 33,34 .…”

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Microscopic annealing process and its impact on superconductivity in T′-structure electron-doped copper oxides

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High-transition-temperature superconductivity arises in copper oxides when holes or electrons are doped into the CuO 2 planes of their insulating parent compounds.While hole-doping quickly induces metallic behavior and superconductivity in many cuprates, electron-doping alone is insufficient in materials such as R 2 CuO 4 (R is Nd, Pr, La, Ce, etc.), where it is necessary to anneal an as-grown sample in a low-oxygen environment to remove a tiny amount of oxygen in order to induce superconductivity. Here we show that the microscopic process of oxygen reduction repairs Cu deficiencies in the as-grown materials and creates oxygen vacancies in the stoichiometric CuO 2 planes, effectively reducing disorder and providing itinerant carriers for superconductivity. The resolution of this long-standing materials issue suggests that the fundamental mechanism for superconductivity is the same for electron-and hole-doped copper oxides.The parent compounds of the high-transition-temperature (high-T c ) copper-oxide superconductors are antiferromagnetic (AF) Mott insulators composed of twodimensional CuO 2 planes separated by charge reservoir layers [1][2][3] . When holes are doped into these planes, the static long-range AF order is quickly destroyed and the lamellar copper-oxide materials become metallic and superconducting over a wide hole-doping range. In the case of electron-doped materials such as the T'-structured R 2 CuO 4 (R is Nd, Pr, La, Ce, etc.), electron-doping alone is insufficient, and annealing the as-grown sample in a low oxygen environment to remove a tiny amount of oxygen is necessary to induce superconductivity 2,3 . Previous work [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] suggests that oxygen reduction may influence mobile carrier concentrations 7 , decrease disorder/impurity scattering 8,10,11,23 , or suppress the long-range AF order 16,17,22 . However, the microscopic process of oxygen reduction, its effect on the large electron-hole phase diagram asymmetry and mechanism of superconductivity 2,3 are still unknown. Here we use x-ray and neutron scattering data, combined with chemical and thermo-gravimetric analysis measurements in the electron-doped Pr 0.88 LaCe 0.12 CuO 4 to show that the microscopic process of oxygen reduction is to repair Cu deficiencies in the as-grown materials 12,13 and to create oxygen vacancies in the stoichiometric CuO 2 (refs. 16,17,22), effectively repairing disorder in the CuO 2 planes and providing itinerant carriers for superconductivity.The role of the reduction process in the superconductivity of electron-doped high-T c copper oxides has been a long-standing unsolved problem. For the hole-doped cuprates, low doping levels (e.g. 5%) entirely suppress AF order and superconductivity appears over a wide range of hole concentrations (from 6% to 30%). In the case of T' structured electron-doped superconductors, doping alone by substituting the trivalent ions R 3+ in R 2 CuO 4 with tetravalent Ce 4+ is insufficient to induce superconductivity a...

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Microscopic annealing process and its impact on superconductivity in T′-structure electron-doped copper oxides

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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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“…We grew large single crystals of Pr 0.88 LaCe 0.12 CuO 4-δ (PLCCO) using the traveling solvent floating zone technique and annealed the samples to obtain optimal superconductivity with T c =24 K (Fig. 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 .…”

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

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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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Neutron Scattering Studies of Antiferromagnetic Correlations in Cuprates

Tranquada

2006

ChemInform

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Electronic inhomogeneity and competing phases in electron-doped superconductingPr0.88LaCe0.12CuO4−δ

Cited by 38 publications

References 35 publications

Microscopic annealing process and its impact on superconductivity in T′-structure electron-doped copper oxides

Microscopic annealing process and its impact on superconductivity in T′-structure electron-doped copper oxides

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

Neutron Scattering Studies of Antiferromagnetic Correlations in Cuprates

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