L. Fruchter, F. Bouquet, Z. Z. Li
A comprehensive study of point contacts made on electron-doped infinite-layer
Sr$_{0.88}$La$_{0.12}$CuO$_2$ thin films is presented. High-impedance contacts
display a contribution from two-level systems (TLS). Some TLS are coupled to
the superconducting condensate, and show an enhanced contribution to the
point-contact resistance in the superconducting state. We propose that this
results from the increase of the TLS relaxation rate, due to its ability to
create pairs of quasiparticles out of the condensate (when located close to the
surface of the film). For low-impedance contacts, Andreev reflection is
observed and we find indications for an order parameter with nodes.
View original:
http://arxiv.org/abs/1201.3790
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