3 research outputs found
Local and macroscopic tunneling spectroscopy of Y(1-x)CaxBa2Cu3O(7-d) films: evidence for a doping dependent is or idxy component in the order parameter
Tunneling spectroscopy of epitaxial (110) Y1-xCaxBa2Cu3O7-d films reveals a
doping dependent transition from pure d(x2-y2) to d(x2-y2)+is or d(x2-y2)+idxy
order parameter. The subdominant (is or idxy) component manifests itself in a
splitting of the zero bias conductance peak and the appearance of subgap
structures. The splitting is seen in the overdoped samples, increases
systematically with doping, and is found to be an inherent property of the
overdoped films. It was observed in both local tunnel junctions, using scanning
tunneling microscopy (STM), and in macroscopic planar junctions, for films
prepared by either RF sputtering or laser ablation. The STM measurements
exhibit fairly uniform splitting size in [110] oriented areas on the order of
10 nm2 but vary from area to area, indicating some doping inhomogeneity. U and
V-shaped gaps were also observed, with good correspondence to the local
faceting, a manifestation of the dominant d-wave order parameter
Thickness independence of field induced time reversal symmetry breaking in Y/sub1 Ba/sub2 Cu/sub3 O/sub7-delta thin films
We have measured the field dependence of the Zero Bias Conductance Peak
(ZBCP) of tunnel junctions prepared on (110) oriented Y1Ba2Cu3O7-d films of
various thickness. We have found that the field splitting of the ZBCP, believed
to be due to the Time Reversal Symmetry Breaking (TRSB) of Andreev surface
bound states, is independent of film thickness. This rules out that Meissner
screening currents are at the origin of TRSB. We conclude that TRSB must,
instead, be due to a field-induced modification of the Order parameter.
Different possibilities involving an imaginary component are discussed.Comment: 7 pages 4 figures submitted to PR