Superconductivity above 20 K in the Ba-K-Bi-O system

Mattheiss, L. F.; Gyorgy, E. M.; Johnson, David W.

doi:10.1103/physrevb.37.3745

Cited by 638 publications

(173 citation statements)

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“…The hole-doped bismuthate Ba 1−x K x BiO 3 (BKBO) has been fascinating researchers since its discovery [1,2] for its diverse physical properties such as superconductivity, metal-insulator transition and charge-density wave (CDW) formation. The crystal structure is a distorted (0 ≤ x < x c ) or cubic (x c < x) three-dimensional perovskite [3], where x c ∼ 0.38.…”

Section: Introductionmentioning

confidence: 99%

Doping dependence of the electronic structure ofBa1−xKxBiO
Kobayashi
¹
,
Mizokawa
²
,
Ino
³

et al. 1999
Phys. Rev. B
16
2
10
0
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We have performed x-ray absorption spectroscopy (XAS) and x-ray photoemission spectroscopy (XPS) studies of single crystal Ba1−xKxBiO3 (BKBO) covering the whole composition range 0 ≤ x ≤ 0.60. Several features in the oxygen 1s core XAS spectra show systematic changes with x. Spectral weight around the absorption threshold increases with hole doping and shows a finite jump between x = 0.30 and 0.40, which signals the metal-insulator transition. We have compared the obtained results with band-structure calculations. Comparison with the XAS results of BaPb1−xBixO3 has revealed quite different doping dependences between BKBO and BPBO. We have also observed systematic core-level shifts in the XPS spectra as well as in the XAS threshold as functions of x, which can be attributed to a chemical potential shift accompanying the hole doping. The observed chemical potential shift is found to be slower than that predicted by the rigid band model based on the band-structure calculations. 71.30.+h,74.25.Jb,74.70.Ad

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Section: Introductionmentioning

confidence: 99%

Doping dependence of the electronic structure ofBa1−xKxBiO
Kobayashi
¹
,
Mizokawa
²
,
Ino
³

et al. 1999
Phys. Rev. B
16
2
10
0
View full text Add to dashboard Cite

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“…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].…”

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
29
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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“…[14] The transition temperature of BKBO is quite high (31 K) in relation to its low density of states at the Fermi level, and it has been suggested [15] that the material is closely related to cuprate high T c superconductors. However the optical properties suggest that they are in fact closer to the conventional BCS superconductors than to the exotic cuprates.…”

Section: B Bcs Superconductors In the Infraredmentioning

confidence: 99%

Infrared properties of exotic superconductors

Timusk

1999

Physica C: Superconductivity

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The infrared spectra of the non-traditional superconductors share certain common features. The lack of a gap signature at 2∆ and the residual conductivity are the consequence of a d-wave order parameter. The high Tc materials, the organic conductors and the heavy Fermion materials have a strong mid-infrared absorption band which can be interpreted as strong coupling of the carriers to electronic degrees of freedom which leads to a breakdown of the Fermi liquid picture. The cuprates and the organic charge transfer salts are unique in possessing an intrinsic low dimensionality. The charge transport normal to the highly conducting direction is incoherent down to the lowest temperatures and frequencies.

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Superconductivity above 20 K in the Ba-K-Bi-O system

Cited by 638 publications

References 10 publications

Doping dependence of the electronic structure ofBa1−xKxBiO
Kobayashi
¹
,
Mizokawa
²
,
Ino
³

et al. 1999
Phys. Rev. B
16
2
10
0
View full text Add to dashboard Cite

Doping dependence of the electronic structure ofBa1−xKxBiO
Kobayashi
¹
,
Mizokawa
²
,
Ino
³

et al. 1999
Phys. Rev. B
16
2
10
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
29
3
19
0
View full text Add to dashboard Cite

Infrared properties of exotic superconductors

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Superconductivity above 20 K in the Ba-K-Bi-O system

Cited by 638 publications

References 10 publications

Doping dependence of the electronic structure ofBa1−xKxBiOKobayashi1, Mizokawa2, Ino3 et al. 1999Phys. Rev. B162100View full textAdd to dashboardCite

Doping dependence of the electronic structure ofBa1−xKxBiOKobayashi1, Mizokawa2, Ino3 et al. 1999Phys. Rev. B162100View full textAdd to dashboardCite

Electron-phonon coupling induced pseudogap and the superconducting transition inBa0.67K0.33BiOChainani1, Yokoya2, Shin3 et al. 2001Phys. Rev. B293190View full textAdd to dashboardCite

Infrared properties of exotic superconductors

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About

Doping dependence of the electronic structure ofBa1−xKxBiO
Kobayashi
¹
,
Mizokawa
²
,
Ino
³

et al. 1999
Phys. Rev. B
16
2
10
0
View full text Add to dashboard Cite

Doping dependence of the electronic structure ofBa1−xKxBiO
Kobayashi
¹
,
Mizokawa
²
,
Ino
³

et al. 1999
Phys. Rev. B
16
2
10
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
29
3
19
0
View full text Add to dashboard Cite