Pseudogap of Optimally Doped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>La</mml:mi></mml:mrow><mml:mrow><mml:mn>1.85</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>Sr</mml:mi></mml:mrow><mml:mrow><mml:mn>0.15</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>CuO</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Observed by Ultrahigh-Resolu

Sato, Takafumi; Yokoya, Takayoshi; Naitoh, Y.; Takahashi, Takashi; Yamada, Kōsaku; Endoh, Y.

doi:10.1103/physrevlett.83.2254

Cited by 84 publications

(42 citation statements)

References 22 publications

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“…Other Raman data show high energy suppression of spectral weight above Tc [4]. In the case of Lal.ssSr0.15CuO4 angle integrated photoemission (PES) reveal a clear pseudogap above Tc with a size of 30-35 meV which is about three times the superconducting gap for this compound [5]. We suggest here that these observations of higher energy pseudogaps are connected to the higher energy dip and hump features found in quasiparticle tunneling spectra.…”

Section: Introductionmentioning

confidence: 68%

High energy secondary peak structure in tunneling spectra (hump) as possible magnetic pseudogap

Zasadzinski

Özyüzer

Miyakawa

et al. 2000

Physica C: Superconductivity

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It is demonstrated that tunneling spectra in various high Tc cuprates display generic features. The principal conductance peaks in superconductor-insulator-normal metal (SIN) junctions indicate the superconducting gap in the density of states (DOS). Higher energy features include a dip and hump structure with a strength that is asymmetric in bias voltage. The dip and hump features follow the doping trends of the superconducting gap, A, with a rough scaling as ,,~2A and ,--3A respectively. Tunneling spectra in underdoped Bi2Sr2CaCu2Os+~ display a more pronounced hump feature suggestive of a second gap in the DOS. It is observed that the hump feature in the tunneling density of states is consistent with other experimental observations of the so-called high energy pseudogap which may have magnetic origins.

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Section: Introductionmentioning

confidence: 68%

High energy secondary peak structure in tunneling spectra (hump) as possible magnetic pseudogap

Zasadzinski

Özyüzer

Miyakawa

et al. 2000

Physica C: Superconductivity

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“…On the other hand, a temperature-dependent pseudogap has been observed in Ba 0.67 K 0.33 BiO 3 , 25 where the energy scale of the pseudogap correlated with the energy of the breathing mode phonon. In the layered Co oxides, the energy scales of ~ 20 meV is comparable to the nearest neighboring magnetic coupling constant J = 10-20 meV as predicted for U dd ~ 5 eV, 7 which has been also concluded from ARPES measurements.…”

mentioning

confidence: 99%

Laser-excited ultrahigh-resolution photoemission spectroscopy ofNaxCoO2·yH2O
Shimojima
¹
,
Yokoya
²
,
Kawamata
³

et al. 2005
Phys. Rev. B
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4
27
0
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We have studied the temperature-dependent electronic structure near the Fermi level (E F ) of the layered cobaltate superconductor, Na 0.35 CoO 2 ·1.3H 2 O, and related materials, using laser-excited ultrahigh-resolution photoemission spectroscopy. We observe the formation of a pseudogap with an energy scale of ~ 20 meV in Na 0.35 CoO 2 ·1.3H 2 O and Na 0.35 CoO 2 ·0.7H 2 O, which is clearly absent in Na 0.7 CoO 2 . The energy scale of the pseudogap is larger than the expected value for the superconducting gap, suggesting an additional competing order parameter at low temperatures. We discuss implications of the pseudogap in relation to available transport and magnetic susceptibility results. 2 Theoretically, recent studies on the Co oxide superconductors have proposed novel superconductivity with various types of order parameters depending on the model used.3 And, several experimental studies have been performed to clarify the symmetry of the superconducting gap. 4 However, agreement on the order parameter has not been reached so far.In the cuprate high temperature superconductors (high-T c 's), whose electronic structure is often described in terms of a quasi-2 dimensional correlated system, understanding the unusual normal state properties has lead to deeper understanding of the superconductivity. Even for the layered Co oxides, recent studies have indicated a rich phase diagram in the non-hydrated Na x CoO 2 system. 5 For superconducting samples, as has been also suggested from theoretical studies, [6][7][8] importance of well-separated Co 3+ and Co 4+ in the superconducting Co oxides has been reported experimentally very recently. 9Coexistence of superconductivity and ordered states have been discussed in cuprate high-T c superconductors.10 In this regard, Na 0.35 CoO 2 ·1.3H 2 O provides another opportunity to investigate charge and/or spin order competing or cooperating with superconductivity in superconducting oxides.Thus, it is essential to study the normal-state electronic structure of the superconducting Co oxides using photoemission spectroscopy (PES), which provides direct information on the electronic structure. Very recent PES studies 9 using hard x-rays (escape depth of ~ 50 Å) have provided bulk fundamental physical parameters that describe the new superconductor in terms of, on-site coulomb energy U dd , charge transfer energy ∆, and hybridization strength V.More importantly, the double-peak structure in the Co 2p core-level spectra revealed charge disproportionation in Na 0.7 CoO 2 and Na 0.35 CoO 2 ·1.3H 2 O samples, which suggest existence of remnant charge order in the superconducting samples. For the states near the Fermi level (E F ), while angle-resolved photoemission spectroscopy (ARPES) studies 11-13 on non hydrated samples showed a large hole pocket around the Γ point in the Brillouin zone, and renormalization on the energy scales of J of ~ 10 meV, 12 no PES study reporting the electronic structure near E F of superconducting Na 0.35 CoO 2 ·1.3H 2 O is reported. Therefore, it is extr...

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“…We note that the pseudogap is a true pseudogap and not extrinsic as the pseudogap is more pronounced at low temperatures when the solid is more conducting, in contrast to the proposal by Joynt [22] for poorly conducting solids. In comparison, a normal phase pseudogap is also observed in the underdoped cuprates [2] but at low energy scales and develops into an anisotropic superconducting gap below T c , although a higher energy scale pseudogap has also been discussed [23,24].…”

mentioning

confidence: 99%

Electron-phonon coupling induced pseudogap and the superconducting transition inBa0.67K0.33BiO
Chainani
¹
,
Yokoya
²
,
Shin
³

et al. 2001
Phys. Rev. B
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30
3
19
0
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We study the single particle density of states (DOS) across the superconducting transition (Tc = 31 K) in single-crystal Ba0.67K0.33BiO3 using ultrahigh resolution angle-integrated photoemission spectroscopy. The superconducting gap opens with a pile-up in the DOS, ∆(5.3 K) = 5.2 meV and 2∆(0)/kB Tc = 3.9. In addition, we observe a pseudogap below and above Tc, occurring as a suppression in intensity over an energy scale up to the breathing mode phonon(∼ 70 meV). The results indicate electron-phonon coupling induces a pseudogap in Ba0. 67K0.33BiO3 . PACS numbers: 74.25.Jb, 74.25.Kc, 79.60.Bm From a variety of experiments and theory, it is clear that the high temperature cuprate superconductors belong to a special class of materials. Some of the important aspects of the cuprates are quasi twodimensionality, short-range antiferromagnetic correlations, an anisotropic pseudogap in the normal phase, and d x 2 −y 2 symmetry of the superconducting gap [1,2]. In contrast, the perovskite series Ba 1−x K x BiO 3 (BKBO) is three-dimensional, contains no transition metal ions, has no magnetic order but still exhibits the highest T c known for an oxide other than the cuprates [3]. The superconductivity in the BKBO series was preceded by the analogous BaBi 1−x Pb x O 3 (BPBO) series which shares the same parent BaBiO 3 (BBO) [4]. The role of electron-phonon coupling in the properties of the BKBO and BPBO series originates in the charge density wave (CDW) state of BBO.The parent BBO is expected to be a metal from band theory with a half-filled Bi 6s band, but the near perfect nesting possible in BBO causes a three-dimensional CDW gap to open up in the DOS [4,5]. The CDW in BBO is coupled to the breathing mode phonon which is due to the contraction and expansion of oxygen octahedra surrounding neighbouring Bi ions. Subtitution with K in the Ba-site results in a semiconductor-metal transition at a critical x c ∼ 0.3. While the CDW state is weakened by substitution, resulting in a systematic lowering of the CDW energy upon doping, the breathing mode phonon is observed even in the metallic phase [6]. Optical conductivity studies [7] suggest remnant local CDW order in the superconducting compositions with x = 0.33 and 0.4. EXAFS measurements[8] also show that there are two types of Bi ions, with short-and long-bond nearest neighbour Bi-O distances. On increasing x, the short and long Bi-O distances become equivalent around x = 0.4. This picture is derived from the formally Bi 3+ and Bi 5+ ions constituting the charge disproportionation in BBO[4], though X-ray and resonant photoemission spectroscopy studies have not shown clear evidence for the same in BBO and the doped compounds [9,10]. The results are understood as due to very small charge transfer between the unequal Bi sites [5]. The crystal structure also evolves with doping and at room temperature, for x = 0.0 -0.1 it is monoclinic, from x = 0.1 to 0.3 it is orthorhombic and above x = 0.3 up to 0.5( = the solubility limit), it is cubic [11].In this work we study the elect...

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Pseudogap of Optimally DopedLa1.85Sr0.15CuO4Observed by Ultrahigh-Resolu

Cited by 84 publications

References 22 publications

High energy secondary peak structure in tunneling spectra (hump) as possible magnetic pseudogap

High energy secondary peak structure in tunneling spectra (hump) as possible magnetic pseudogap

Laser-excited ultrahigh-resolution photoemission spectroscopy ofNaxCoO2·yH2O
Shimojima
¹
,
Yokoya
²
,
Kawamata
³

et al. 2005
Phys. Rev. B
Self Cite
30
4
27
0
View full text Add to dashboard Cite

Electron-phonon coupling induced pseudogap and the superconducting transition inBa0.67K0.33BiO
Chainani
¹
,
Yokoya
²
,
Shin
³

et al. 2001
Phys. Rev. B
Self Cite
30
3
19
0
View full text Add to dashboard Cite

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Pseudogap of Optimally DopedLa1.85Sr0.15CuO4Observed by Ultrahigh-Resolu

Cited by 84 publications

References 22 publications

High energy secondary peak structure in tunneling spectra (hump) as possible magnetic pseudogap

High energy secondary peak structure in tunneling spectra (hump) as possible magnetic pseudogap

Laser-excited ultrahigh-resolution photoemission spectroscopy ofNaxCoO2·yH2OShimojima1, Yokoya2, Kawamata3 et al. 2005Phys. Rev. BSelf Cite304270View full textAdd to dashboardCite

Electron-phonon coupling induced pseudogap and the superconducting transition inBa0.67K0.33BiOChainani1, Yokoya2, Shin3 et al. 2001Phys. Rev. BSelf Cite303190View full textAdd to dashboardCite

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Product

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About

Laser-excited ultrahigh-resolution photoemission spectroscopy ofNaxCoO2·yH2O
Shimojima
¹
,
Yokoya
²
,
Kawamata
³

et al. 2005
Phys. Rev. B
Self Cite
30
4
27
0
View full text Add to dashboard Cite

Electron-phonon coupling induced pseudogap and the superconducting transition inBa0.67K0.33BiO
Chainani
¹
,
Yokoya
²
,
Shin
³

et al. 2001
Phys. Rev. B
Self Cite
30
3
19
0
View full text Add to dashboard Cite