Superconducting-plasma resonance along the c axis in various copper oxide superconductors

H. Shibata; T. Yamada

doi:10.1103/PhysRevB.54.7500

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Superconducting-plasma resonance along the c axis in various copper oxide superconductors

H. Shibata, T. Yamada

DOI 10.1103/PhysRevB.54.7500 · Physical Review B

T1

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Abstract

Superconducting plasma along the c axis in the far-infrared region are observed in various high-Tc cuprates including electron-doped and Bi cuprates. It is shown that the sphere resonance of the powder samples occurs near the frequency where the plasma along the c axis exists, since it is only sensitive to the c-axis dielectric constant in the far-infrared region due to the metal-like property in the ab plane. This method provides an alternative to the reflectivity measurement of single crystals for investigating the plasma along the c axis. By measuring down to 7.5 cm−1, the resonance is observed in Bi1.85Pb0.35Sr2Ca2Cu3.1Oy, La1.82Ca1.18Cu2O6+δ, (Nd0.66Sr0.205Ce0.135)2CuO4 (T* phase), (Ba0.56Sr0.44)2Cu1.1O2.2+δ(CO3)0.9, Pr1.85Ce0.15CuO4, and Nd2CuO4−xFx. Among the Bi cuprates, however, no resonance is observed in Bi2Sr2CaCu2Oy and Bi2Sr1.6La0.4CuOy in this frequency region, which suggests that the resonance exists below 7.5 cm−1. The resonance frequencies are discussed based on the Josephson-coupled layer model, and the c-axis penetration depth λc are estimated from the resonance frequencies. It appears that λc depends on the insulating nature of the barrier layer between CuO2 planes. Substitution effects on the resonance are also investigated in La2−xSrx(Cu1−zZnz)O4, Nd1.85Ce0.15(Cu1−zZnz)O4, and YBa2(Cu1−zCoz)3O6+δ, and compared to the results of YBa2(Cu1−zZnz)3O6+δ. Through the substitution, the resonance frequencies strongly decrease for all samples, indicating the strong increase of λc. The frequency decrease in YBa2(Cu1−zCoz)3O6+δ suggests that the resonance frequency is determined by the barrier at the (BaO)[Cu(1)Oδ](BaO) chain layer, not at the Y layer. © 1996 The American Physical Society.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Bi1.85Pb0.35Sr2Ca2Cu3.1Oy Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	107	Pressure not reported	midpoint
La1.82Ca1.18Cu2O6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	52	Pressure not reported	midpoint
Nd0.66Sr0.205Ce0.135)2CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	24	Pressure not reported	midpoint
Ba0.56Sr0.44)2Cu1.1O2.2CO3)0.9 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	35	Pressure not reported	midpoint
Pr1.85Ce0.15CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	20	Pressure not reported	midpoint
Nd2CuO4xFx Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	22	Pressure not reported	midpoint