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Shen, Z.‐X.; Dessau, D. S.; Wells, B. O.; King, David M.; Spicer, W. E.; Arko, A. J.; Marshall, D. S.; Lombardo, L. W.; Kapitulnik, A.; Dickinson, P. H.; Doniach, Sebastian; DiCarlo, Jeffrey M.; Loeser, T.; Park, C. H.

doi:10.1103/physrevlett.70.1553

Cited by 876 publications

(301 citation statements)

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“…1,2 One question that arises is whether the pairing symmetry is affected by doping. The symmetry of the superconducting order parameter for the optimally doped HTS's is consistent with d x 2 Ϫy 2( d-wave͒ as found in angle-resolved photoemission spectroscopy 3,4 ͑ARPES͒ experiments on Bi 2 Sr 2 CaCu 2 O 8ϩ␦ ͑Bi-2212͒ and tricrystal ring 5,6 experiments on YBa 2 Cu 3 O 7Ϫx and Tl 2 Ba 2 CuO 6ϩ␦ . The possibility of gap symmetry conversion from d-wave to s-wave with overdoping of Bi-2212 is suggested by Kendziora et al 7 and Kelley et al 8 using Raman and ARPES studies respectively.…”

Section: Introductionsupporting

confidence: 52%

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Quasiparticle and Josephson tunneling of overdopedBi2Sr2CaCu2<

2000

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The point contact tunneling technique is used to examine quasiparticle and Josephson currents in overdoped Bi 2 Sr 2 CaCu 2 O 8ϩ␦ ͑Bi-2212͒ single crystals with bulk T c values ranging from 82 K down to 62 K. Superconductor-insulator-normal-metal ͑SIN͒ tunnel junctions are formed between Bi-2212 crystals and a Au tip, which display well-resolved quasiparticle gap features including sharp conductance peaks. Reproducible superconductor-insulator-superconductor ͑SIS͒ tunnel junctions are also obtained between two pieces of the Bi-2212 crystals, resulting in simultaneous quasiparticle and Josephson currents. The dynamic conductances of both SIN and SIS junctions are qualitatively similar to those found on optimally doped Bi-2212, but with reduced gap values, e.g., ⌬ϭ15-20 meV for T c ϭ62 K. Fits to the conductance data in the gap region are obtained using a model with d x 2 Ϫy 2 symmetry, and it is shown that this provides a better fit than s-wave symmetry. Both SIN and SIS tunneling conductances also display dip and hump features at high bias voltages similar to those found on optimal and underdoped crystals, indicating that these are intrinsic properties of the quasiparticles. The SIS data indicate that these features appear to be part of a larger spectrum that extends out to 300-400 mV. The Josephson current has been measured for 13 SIS junctions on the 62 K crystals with resistances varying over two decades. It is found that the maximum value depends on junction resistance in a manner consistent with Ambegaokar-Baratoff theory, but with a reduced I c R n product.

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Section: Introductionsupporting

confidence: 52%

“…13 The dip and hump features may be indications of such quasiparticle decay processes as is suggested in ARPES. 3,4 …”

Section: Results Of Sin Junctionsmentioning

confidence: 99%

Quasiparticle and Josephson tunneling of overdopedBi2Sr2CaCu2<

2000

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“…In optimally hole-doped cuprates, the SC gap function has a d-wave symmetry in momentum (k) space 5 . Its size evolves smoothly along the Fermi surface (FS) from zero at locations referred to as nodes to a large maximum ∆ at the 'antinodes' that puts the value of 2∆/k B T c in the strong coupling regime 6,7 . In contrast, angle-resolved photoemission spectroscopy (ARPES) studies on optimally hole-doped pnictide Ba 0.6 K 0.4 Fe 2 As 2 (T c = 37 K; labelled as OPD37K), have revealed isotropic gaps that have different values on different FSs [8][9][10][11] , with strong pairing occurring on the quasi-(or nearly) nested FSs.…”

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confidence: 99%

Fermi surface dichotomy of the superconducting gap and pseudogap in underdoped pnictides

Richard

Nakayama

et al. 2011

Nat Commun

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High-temperature superconductivity in iron-arsenic materials (pnictides) near an antiferromagnetic phase raises the possibility of spin-fluctuation-mediated pairing. However, the interplay between antiferromagnetic fluctuations and superconductivity remains unclear in the underdoped regime, which is closer to the antiferromagnetic phase. Here we report that the superconducting gap of underdoped pnictides scales linearly with the transition temperature, and that a distinct pseudogap coexisting with the superconducting gap develops on underdoping. This pseudogap occurs on Fermi surface sheets connected by the antiferromagnetic wavevector, where the superconducting pairing is stronger as well, suggesting that antiferromagnetic fluctuations drive both the pseudogap and superconductivity. Interestingly, we found that the pseudogap and the spectral lineshape vary with the Fermi surface quasi-nesting conditions in a fashion that shares similarities with the nodal-antinodal dichotomous behaviour observed in underdoped copper oxide superconductors.

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“…Angle-resolved photoemission measurements in the superconducting state have revealed a quasiparticle spectrum with a d-wave gap structure that exhibits a maximum along the antinodal direction and vanishes along the nodal direction 1 . Subsequent measurements have shown that, at low doping levels, this gap structure persists even in the high-temperature metallic state, although the nodal points of the superconducting state spread out in finite 'Fermi arcs' 2 .…”

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confidence: 99%

Nodal quasiparticle in pseudogapped colossal magnetoresistive manganites

Mannella

Yang

Zhou

et al. 2005

Nature

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A characteristic feature of the copper oxide high-temperature superconductors is the dichotomy between the electronic excitations along the nodal (diagonal) and antinodal (parallel to the Cu-O bonds) directions in momentum space, generally assumed to be linked to the 'd-wave' symmetry of the superconducting state. Angle-resolved photoemission measurements in the superconducting state have revealed a quasiparticle spectrum with a d-wave gap structure that exhibits a maximum along the antinodal direction and vanishes along the nodal direction 1 . Subsequent measurements have shown that, at low doping levels, this gap structure persists even in the high-temperature metallic state, although the nodal points of the superconducting state spread out in finite 'Fermi arcs' 2 . This is the so-called pseudogap phase, and it has been assumed that it is closely linked to the superconducting state, either by assigning it to fluctuating superconductivity 3 or by invoking orders which are natural competitors of d-wave superconductors 4,5 . Here we report experimental evidence that a very similar pseudogap state with a nodal-antinodal dichotomous character exists in a system that is markedly different from a superconductor: the ferromagnetic metallic groundstate of the colossal magnetoresistive bilayer manganite La 1.2 Sr 1.8 Mn 2 O 7 . Our findings therefore cast doubt on the assumption that the pseudogap state in the copper oxides and the nodal-antinodal dichotomy are hallmarks of the superconductivity state. La 1.2 Sr 1.8 Mn 2 O 7 (LSMO) is a prototypical bilayer manganite that exhibits the colossal magnetoresistance (CMR) effect-the extremely large drop in resistivity induced by application of a magnetic field near the Curie temperature (T C ) 6,7 . The CMR effect exploits a metalinsulator transition between a low-temperature ferromagnetic-metallic ground state and a high-temperature paramagnetic-insulating phase. The nature of the ferromagnetic-metallic ground state in LSMO remains highly controversial. On the one hand, the underlying Fermi surface and band structure have clear resemblance to those of the copper oxides 8 (Lin, H., Sahrakorpi, S., Barbiellini, B. & Bansil, A., personal communication on full potential band structure and Fermi surface computations for x ¼ 0.4). On the other hand, previous angle-resolved photoemission (ARPES) investigations revealed no quasiparticle peak, a suppression of spectral weight at the Fermi level (E F ) (the pseudogap), and an unusually light effective mass, a factor of two lighter than the calculated band structure value. This last observation is puzzling given the general expectation of strong interactions in the manganites. Moreover, the value for the inplane conductivity calculated with the ARPES parameters is nearly one order of magnitude higher than that measured by transport 9-11 .Our ARPES experiments resolve the controversy of the lowtemperature ferromagnetic-metallic groundstate of LSMO by demonstrating that its electronic structure is strikingly similar to that found in th...

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Anomalously large gap anisotropy in thea-bplane ofBi2Sr2

Cited by 876 publications

References 23 publications

Quasiparticle and Josephson tunneling of overdopedBi2Sr2CaCu2<

Quasiparticle and Josephson tunneling of overdopedBi2Sr2CaCu2<

Fermi surface dichotomy of the superconducting gap and pseudogap in underdoped pnictides

Nodal quasiparticle in pseudogapped colossal magnetoresistive manganites

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