One of the mysteries of modern condenced-matter physics is the nature of the pseudogap state of the superconducting cuprates. Kaminski et al.1 claimed to have observed signatures of time-reversal symmetry breaking in the pseudogap regime in underdoped Bi2Sr2CaCu2O8+d (Bi2212). Here we argue that the observed dichroism is due to the 5x1 superstructure replica of the electronic bands and therefore cannot be considered as evidence for the spontaneous time-reversal symmetry breaking in cuprates.
@article{arxiv.cond-mat/0402251,
title = {Time-reversal symmetry breaking versus superstructure},
author = {S. V. Borisenko and A. A. Kordyuk and A. Koitzsch and M. Knupfer and J. Fink},
journal= {arXiv preprint arXiv:cond-mat/0402251},
year = {2009}
}