Abstract

Recent pulsed-X-ray, pulsed-magnetic-field measurements (Gerber et al. arXiv :1506.07910) have revealed a new high-field CDW structure in underdoped YBCO . We have extended these measurements in static (but not so high) fields to give a more detailed picture of the high-field structure and field-temperature-doping phase diagram, as well as how they evolve out of the low field structure (Chang et al., in preparation). Comparison with our CDW structure determination at zero field (Forgan et al. arXiv:1504.01585) allows us to determine the symmetry of the CDW in the high-field phase. With this new information, we can include CDW and spin-orbit (S-O) interactions in a tight-binding representation of the electronic structure in the CuO2 planes to calculate the expected reconstruction of the Fermi surface sheets (Briffa et al., in preparation). These calculations reveal that magnetic breakdown across small gaps and spin-flips due to S-O are important features (see also Harrison et al. Sci. Rep. 5, 10914 (2015)). It appears that our minimal Fermi liquid approach can account for the quantum oscillation and other experimental data in the underdoped state of this benchmark cuprate, although some fascinating questions remain.