Triplanar model for the gap and penetration depth inYBa2Cu3

Abstract

YBaCuO 7 is a trilayer material with a unit cell consisting of a CuO 2 bilayer with a CuO plane of chains in between. Starting with a model of isolated planes coupled through a transverse matrix element, we consider the possibility of intra-as well as interplane pairing within a nearly antiferromagnetic Fermi-liquid model. Solutions of a set of three coupled BCS equations for the gap exhibit orthorhombic symmetry with s-as well as d-wave contributions. The temperature dependence and a-b in-plane anisotropy of the resulting penetration depth is discussed and compared with experiment. ͓S0163-1829͑97͒06110-9͔

Magnetic field as a probe of gap energy scales inYBa2Cu3O7Whelan1, Ćarbotte2 2000Phys. Rev. BSelf Cite5240View full textAdd to dashboardCite

“…1 using s = 0.57 (this choice is explained below.) There is a van Hove singularity at ω = (1+|s|)∆ 0 as we expect [10], however there is another at (1 − |s|)∆ 0 , in qualitative agreement with [2,3]. A problem with the measured N (ω) is that there is a large zero bias anomaly in contradiction with theory and presumably arising from surface effects.…”

Phenomenological description of the microwave surface impedance and complex conductivity of high-T c single crystals

“…Recently, observations of unusual microwave properties of HTS materials have caught the attention of a number of researchers [43][44][45][46][47]55,56 . These observations are tenta-tively attributed to mixed (d + s)-wave symmetry of the order parameter.…”

“…However, none of these theories can explain substantially different slopes of ∆λ ab (T ) at low T of YBCO samples grown by different methods 40 nor features, such as a bump 9,11,16,41 or a plateau 8,10,12 , observed in the intermediate temperature range 0.3 T c < T < 0.8 T c . Models containing a mixed (d + s) symmetry of the order parameter [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] hold some promise for a successful description of these experimental features, but this would require additional theoretical investigations.…”

Effect of the pseudogap on the temperature dependence of the magnetic penetration depth in YBCO films

“…Pos-sible anomalous behavior of the quasi-1D CuO chains [19] is not included. Because such behavior is not observed in untwinned crystals, it is likely that chain specific effects are negligible in our highly twinned films.…”