Microwave penetration depth measurements onBi2Sr2

Abstract

The temperature dependence of the magnetic penetration depth of Bi2Sr2CaCu20g single crystals and YBa2Cii307-s thin films has been measured with a parallel plate resonator technique at microwave frequencies. Both materials show a T 2 temperature dependence between 10 and 25 K, and systematic deviations towards a flatter temperature dependence below 10 K. We have also calculated the real part of the complex conductivity of YBa2Cu307-$ thin films from our penetration depth and surface resistance data and compare them with those of YBa2Cu3C>7-a single crystals.

Power-law low-temperature asymptotics for spatially nonhomogeneous s-wave superconductors

“…For nominally pure YBa 2 Cu 3 O 7−x samples linear dependences on T are observed [29], whereas for Znand Ni-doped as well as nonhomogeneous crystals δ λ L ∝ T 2 [29][30][31][32][33] in a formal accordance with the theory of d-wave superconductors, either dirty ones [4] or those with surface-induced Andreev bound states [33]. There are also data showing two-gap low-T asymptotics of δ λ L (T) in YBa 2 Cu 3 O 7−x [34].…”

Linear temperature variation of the penetration depth in YBa 2 Cu 3 O 7 − δ thin films

“…While in the BCS weak coupling theory, the penetration depth λ(T ) varies as exp(−∆/k B T ), a quadratic behavior λ(T ) ∼ T 2 was reported by many groups in YBCO thin films [1][2][3]. Recently, in very high quality YBCO single crystals, a linear temperature dependence was measured up to 40 K [4][5][6].…”

Electrical Conductivity and Magnetic Susceptibility of Thallium 1223-Based Superconductor in the Fluctuation Range

“…A crossover from 2D to 1D was also reported for Hg-Tl 1223 ceramic superconductor [27]. The excess conductivity of the lower-dimensionality superconductors could successfully be described by the theory [28], which predicts λ = 1 for the two-dimensional and λ = 1.5 for the one-dimensional case in (1).…”

“…When we approach the critical temperature from above, normal areas become small islands. A large penetration depth λ of 10 3 -10 4Å [1], small coherence length ξ of 10Å [2], high anisotropy [3,4] as well as high critical temperatures considerably enhance the role of thermal fluctuations in high-temperature superconductors (HTS). After the discovery of HTS, papers treating thermal fluctuation problems appeared, in which the excess conductivity in the transition ranges for yttrium- [5][6][7], bismuth- [8,9], and thallium [10][11][12]-based superconductors was most often studied.…”