London Penetration Depth as a Test of Order Parameter Symmetry in Sodium Cobaltate Superconductors

Dzebisashvili, Dmitry M.; Klyuchantsev, Andrey B. Source: SYMMETRY-BASEL, 11 (5):10.3390/sym11050633 MAY 2019

Temperature dependence of the magnetic field penetration depth λ was calculated for water intercalated sodium cobaltate superconductor Na x CoO 2y H 2 O. Assuming that the system is in the chiral d+id–wave superconducting state, it was shown that the shifting of the excitation spectrum nodal points off the normal phase Fermi surface due to variation of the sodium content x changes the functional form of the temperature dependence of λ2 from exponential to linear in the low temperatures region. It is argued that this change in the functional form of T–dependence of the λ2 can serve as a proof for the chiral symmetry of the superconducting order parameter in the sodium cobaltate.