"Magneto-Optical Measurements of a Cascade of Transitions in Superconducting La1.875Ba0.125CuO4 Single Crystals"

Hovnatan Karapetyan: M. Hücker, G. D. Gu, J. M. Tranquada, M. M. Fejer, Jing Xia, and A. Kapitulnik; Physical Review Letters, 10/02/12.

Additional Authors: M. Hücker, G. D. Gu, J. M. Tranquada, M. M. Fejer, Jing Xia, and A. Kapitulnik

Abstract:

Recent experiments on the original cuprate high-temperature superconductor, La2-xBaxCuO4, revealed a remarkable sequence of phase transitions. Here we investigate such crystals with the polar Kerr effect, which is sensitive to time-reversal-symmetry breaking. Concurrent birefringence measurements accurately locate the structural phase transitions from high-temperature tetragonal to low-temperature orthorhombic, and then to lower-temperature tetragonal, at which temperature strong Kerr signal onsets. Hysteretic behavior of the Kerr signal suggests that time-reversal symmetry is already broken well above room temperature, an effect that was previously observed in high quality YBa2Cu3O6+x crystals.