Polar Kerr-effect measurements of the high-temperature YBa2Cu3O6+x superconductor: evidence for broken symmetry near the pseudogap temperature.
The polar Kerr effect in the high-T_(c) superconductor YBa2Cu3O6+x was measured at zero magnetic field with high precision using a cyogenic Sagnac fiber interferometer. We observed nonzero Kerr rotations of order approximately 1 microrad appearing near the pseudogap temperature T(*) and marking what appears to be a true phase transition. Anomalous magnetic behavior in magnetic-field training of the effect suggests that time reversal symmetry is already broken above room temperature.
Department of Physics, Stanford University, Stanford, California 94305, USA.
Jing
J
Xia
Elizabeth
E
Schemm
G
G
Deutscher
S A
SA
Kivelson
D A
DA
Bonn
W N
WN
Hardy
R
R
Liang
W
W
Siemons
G
G
Koster
M M
MM
Fejer
A
A
Kapitulnik