sensitive measurements of
the in-plane gap symmetry
We have determined the position of the
in-plane nodes in YBCO, and confirmed the small size, if any, of an imaginary component to the gap, by imaging the
presence or absence of the half-flux quantum effect in a series of 2-junction YBCO-Nb rings with varying junction angles
relative to the YBCO crystalline axes.
"Angle-resolved phase-sensitive determination of the in-plane gap symmetry in YBa2Cu3O7", J. R. Kirtley, C. C. Tsuei, A. Ariando, C. J. M. Verwijs, S. Harkema and H. Hilgenkamp, Nature Physics 2 , 190 (2006).