Temperature dependence of the half-integer magnetic flux quantum

The temperature dependence of the half-integer magnetic flux quantum effect in thin-film tricrystal samples of the high-critical-temperature cuprate superconductor YBa2Cu3O(7-δ) was measured and found to persist from a temperature of 0.5 kelvin through a critical temperature of about 90 kelvin, with no change in total flux. This result implies that d-wave symmetry pairing predominates in this cuprate, with a small component of time-reversal symmetry breaking, if any, over the entire temperature range.