Search for circular dichroism in high-Tc superconductors

We report observation of circular dichroism in reflection from various cuprate superconducting materials, including YBa{sub 2}Cu{sub 2}O{sub 7{minus}{ital x}} films, an etched YBa{sub 2}Cu{sub 3}O{sub 7} crystal, and a Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} crystal. This signal develops as {ital T} is lowered below 200 K and exhibits little change near {ital T}{sub {ital c}}. The exact onset temperatures differ for the various materials.