Dependence of superconducting properties on the Cu-valence determined by iodometry in HgBa2CuO4+δ

Fukuoka, A.; Tokiwa‐Yamamoto, A.; Itoh, Makoto; Usami, R.; Adachi, Seiji; Yamauchi, H.; Tanabe, K.

doi:10.1016/0921-4534(96)00288-2

Cited by 65 publications

(28 citation statements)

References 13 publications

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“…This phase transition line T c (x), separating the superconducting from the normal conducting phase, appears to be a generic property of cuprate superconductors. In La 2−x Sr x CuO 4 , HgBa 2 CuO 4+x [19,20] [23], only the underdoped and optimally doped regimes appear to be accessible. As shown in Fig.1 for La 2−x Sr x CuO 4 the effective mass anisotropy, measured in terms of γ = M c /M ab increases drastically by approaching the underdoped limit.…”

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confidence: 99%

Isotope Effects in Underdoped Cuprate Superconductors: A Quantum Critical Phenomenon

Schneider

Keller

2001

Phys. Rev. Lett.

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We show that the unusual doping dependence of the isotope effects on transition temperature and zero temperature in -plane penetration depth naturally follows from the doping driven 3D-2D crossover, the 2D quantum superconductor to insulator transition (QSI) in the underdoped limit and the change of the relative doping concentration upon isotope substitution. Close to the QSI transition both, the isotope coefficient of transition temperature and penetration depth approach the coefficient of the relative dopant concentration, and its divergence sets the scale. These predictions are fully consistent with the experimental data and imply that close to the underdoped limit the unusual isotope effect on transition temperature and penetration depth uncovers critical phenomena associated with the quantum superconductor to insulator transition in two dimensions. PACS numbers: 74.20. Mn, 74.25Dw, The observation of an unusual isotope effect in underdoped cuprate superconductors on transition temperature [1][2][3] and zero temperature penetration depth [4][5][6][7] poses a challenge to the understanding of high temperature superconductivity. In this letter we show that this behavior naturally follows from the doping driven 3D-2D crossover, the 2D superconductor to insulator (QSI) transition in the underdoped limit and the change of the relative doping concentration upon isotope substitution. Thus, the unusual isotope effect on superconducting properties of underdoped cuprates is derived to be a quantum critical phenomenon driven by variation of the dopant concentration.Consider [23], only the underdoped and optimally doped regimes appear to be accessible. As shown in Fig.1 for La 2−x Sr x CuO 4 the effective mass anisotropy, measured in terms of γ = M c /M ab increases drastically by approaching the underdoped limit. This property, also observed in HgBa 2 CuO 4+δ [20] and YBa 2 Cu 3 O 7−x [22], appears to be generic and reveals the crossover from three (3D) to two dimensional (2D) behavior.In our considerations the starting point is the critical endpoint of the phase transition line T c (x), where at T = 0 and x = x u , driven by variation of the dopant concentration x, the QSI transition occurs. Close to this critical endpoint the bulk superconductors correspond to a stack of independent superconducting slabs of thickness d s . Moreover, close to such a critical point, low energy properties depend only on the spatial dimensionality of the system, the number of components of the order parameter and the range of the interaction. The theory of quantum critical phenomena predicts that the transition temperature and zero temperature in -plane penetration depth scale as [24,17,18] z is the dynamic critical exponent, ν the exponent of the diverging length, a and b nonuniversal critical amplitudes, andmeasures the distance from the quantum critical point at x u , where in cuprate superconductors the QSI transition occurs. For a complex scalar order parameter and in D=2 the critical amplitudes a and b and the slab thickness d s ...

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confidence: 99%

Isotope Effects in Underdoped Cuprate Superconductors: A Quantum Critical Phenomenon

Schneider

Keller

2001

Phys. Rev. Lett.

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“…The interstitial oxygen excess atom is placed in the Hg plane that forms the top and bottom of the unit cell (HgO δ ). Synthesizing single-phase Hg-1201 compounds with various oxygen contents over a range of 4.03-4.14 showed a maximum T c = 95 ± 1 K at an optimized doping level of δ 1 ≈ 0.08 [4,8]. The excess oxygen was homogeneously distributed.…”

Section: Hbcco Familymentioning

confidence: 91%

“…The HTSC unit area has four doped unit cells with Cu 3+ -ions at its corners counting as one doped element, and the doping density is thus given by ( ) −1 . The optimum oxygen excess value is derived from the bell-shaped T c versus δ 1 curve, which is centered at δ 1 = 0.0825 ± 0.005 [8]. This results in a doping density of ( ) −1 = (4 + δ 1 )/4 − 1 ≡ 2.06%.…”

Section: Hbcco Familymentioning

confidence: 99%

Electronic Energy Levels in High-Temperature Superconductors

Roeser

Haslam

Lopez

et al. 2010

J Supercond Nov Magn

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Parent materials of high-temperature superconductors (HTSC) need to be doped to become superconducting. The optimum doping for maximum critical transition temperature T c has been analyzed for more than 20 materials. Assuming a uniform doping distribution the distance x between doped unit cells-projected into the CuO 2 plane for cuprates-shows a strong linear correlation to the inverse of T c in the form (2x) 2 = m 1 1/T c with a slope of m 1 = (2.786 ± 0.029) × 10 −15 m 2 K. The mercury cuprate homologous series HgBa 2 Ca n − 1 Cu n O 2n+2+δ with n = 1, 2, 3 has been used to demonstrate the procedure deriving the doping distance x from the optimum doping value δ.

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“…Therefore, an estimation of the dopant concentration, δ PAC , within the 199m Hg probing sample region will be performed. It is reported that T C has a cupolalike dependence with doping (δ), where δ opt ∼0.22(4) 28,29,34,35 and δ max ∼0.30(3) 28,29,34,35 . From XRD measurements, the present samples after synthesis have δ=0.22(3) which is in good agreement with the optimal doping for this compound.…”

Section: Discussionmentioning

confidence: 99%

Oxygen ordering in the high-Tcsuperconductor HgBa2CaCu2O
Mendonça
¹
,
Correia
²
,
Haas
³

et al. 2011
Phys. Rev. B

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Lattice sites and collective ordering of oxygen atoms in HgBa2CaCu2O 6+δ were studied using the Perturbed Angular Correlation (PAC) technique at ISOLDE/CERN. The electric field gradients (EFG) at 199m Hg nuclei have been measured as function of oxygen doping on the Hg planes, above and below TC. In comparison with the results obtained for oxygen and fluorine doping in Hg-1201, the analysis shows a different oxygen ordering exhibited by Hg-1212. Moreover, for all studied cases, the experimental results show that at a local scale there is non-uniform oxygen distribution.A series of ab-initio EFG calculations allowed to infer that at low concentrations, regions without oxygen coexist with regions where O 2δ dumbbell molecules are located at the centre of the Hg mesh. On the other side, at high concentrations, O 2δ dumbbell molecules coexist with single O δ atoms occupying the centre of the Hg mesh.

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Dependence of superconducting properties on the Cu-valence determined by iodometry in HgBa2CuO4+δ

Cited by 65 publications

References 13 publications

Isotope Effects in Underdoped Cuprate Superconductors: A Quantum Critical Phenomenon

Isotope Effects in Underdoped Cuprate Superconductors: A Quantum Critical Phenomenon

Electronic Energy Levels in High-Temperature Superconductors

Oxygen ordering in the high-Tcsuperconductor HgBa2CaCu2O
Mendonça
¹
,
Correia
²
,
Haas
³

et al. 2011
Phys. Rev. B

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Dependence of superconducting properties on the Cu-valence determined by iodometry in HgBa2CuO4+δ

Cited by 65 publications

References 13 publications

Isotope Effects in Underdoped Cuprate Superconductors: A Quantum Critical Phenomenon

Isotope Effects in Underdoped Cuprate Superconductors: A Quantum Critical Phenomenon

Electronic Energy Levels in High-Temperature Superconductors

Oxygen ordering in the high-Tcsuperconductor HgBa2CaCu2OMendonça1, Correia2, Haas3 et al. 2011Phys. Rev. B

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Oxygen ordering in the high-Tcsuperconductor HgBa2CaCu2O
Mendonça
¹
,
Correia
²
,
Haas
³

et al. 2011
Phys. Rev. B