Angular dependence of the magnetoresistance in HgBa₂CuO_4+δ<u> </u>

The Fermi surface in the cuprates is known to undergo significant changes with temperature and doping, from Fermi arcs to small pockets reconstructed by charge density wave order. In general the shape of the Fermi surface for a particular phase reveals information about its place in the phase diagram; for example, the symmetries broken by the charge density wave. Such information is valuable to understanding the relationship of these phases to high temperature superconductivity. The pseudogap phase is of particular interest because superconductivity and the charge density wave emerge from this phase as temperature is lowered.

Here we present measurements of the angular dependence of the c-axis magnetoresistance in the pseudogap regime of underdoped single layer cuprate HgBa₂CuO_4+δ. We have performed transport measurements up to 65 T at many angles of the c-axis with respect to the applied field. From this data we are able to extract details about the structure of the Fermi surface in the pseudogap regime and discuss its morphology.