a-b Plane Anisotropy in YBCO

Authors: W. ATKINSON, J.P. CARBOTTE, C. O'DONOVAN

Abstract: The zero temperature in plane penetration depth in an untwinned single crystal of optimally doped YBa_2Cu_3O_{6.93} is highly anisotropic. This fact has been interpreted as evidence that a large amount of the condensate resides in the chains. On the other hand, the temperature dependence of \lambda_a(T)/\lambda_a(0) and \lambda_b(T)/\lambda_b(0) (where the b-direction is along the chains) are not very different. This constrains theories and is, in particular, difficult to understand within a proximity model with d-wave pairing only in the CuO_2 plane and none on the CuO chains but instead supports a more three dimensional models with interplane interactions.

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