Penetration depth anisotropy in cuprates with pseudogap

Abstract

AbstractWe study the penetration depths along the a (λa), b (λb) and c (λc)‐axes in the presence of the pseudogap and d superconducting phases (DSC) in a simple model for cuprates. The pseudogap phase is addressed within the framework of the ordered d ‐density wave (DDW). The above scenario is considered using a mean‐field calculation of the tight binding model which incorporates two layers – a CuO2 plane and a CuO chain per unit cell. The CuO chains become superconducting due to the proximity to the planes below the critical temperature. Moreover our model includes a momentum dependent chain‐plane coupling. We observe distinct behaviors for the penetration depth results along the three directions which is consistent with the anisotropy observed in the experimental results. The temperature dependence of λc is ex‐ actly the same as that of the recent experimental results as demonstrated for Tc = 18 K in the underdoped region. We observe a qualititave difference in the temperature dependence of λa and λb when compared to our previous studies. However the phase diagram due to the inclusion of the momentum dependence of the coupling suffers no significant variation. The main result of our work then is that a simple proximity DDW model in which the pairing interaction is localized to the planes and the planes are coupled to the chains through a momentum dependent term can account for many observed experimental properties. The inclusion of the pseudogap and also the value of the chain‐plane coupling modifies the general trend of our results when compared to the simple DSC model without the coupling. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)