We have measured the amount of nonreciprocal circular birefringence of 50 to 800 A YBa2Cu3C>7 films in transmission with a 15-j/m beam diameter. A novel instrument with a sensitivity of 2 //rad for nonreciprocal phase shifts was developed by modifying a fiber-optic gyroscope. It is insensitive to reciprocal phase shifts. We observed no nonreciprocal phase shifts in any samples.PACS numbers: 74.65.+nOne of the most exciting proposals for the theory of the cuprate high-temperature superconductors (HTSC) is the so-called "anyon superconductivity." 1 " 3 This theory is based on the concept that in two spatial dimensions, one can obtain not only quantum ideal Bose and Fermi gases, but also quantum ideal gases of new types of particles that interpolate between those two extremes, and hence obey fractional statistics. Those particles are known generically as anyons. It was first pointed out by Laughlin and co-workers 4~6 that these gases form superfluids, and become superconductors if the anyons are electrically charged. A striking property of such a superconductor is that its ground state exhibits violation of parity (P) and time-reversal (T) symmetries. 3 Similar to a magnetic material, an anyon superconductor will exhibit a spontaneous Hall effect and magneto-optical effects. If the cuprates are indeed anyon superconductors then in a transmission experiment through a thin HTSC film, one expects to observe a nonreciprocal rotation of polarization equivalent to the Faraday effect. In reflection, one expects to see an effect resembling the polar Kerr effect. Both effects are nonreciprocal as a consequence of the breakdown of time-reversal symmetry. 1 ' 3In a recent experiment, Lyons et al. 1 reported such nonreciprocal optical effects in reflection from various HTSC. They constructed an optical system to measure the circular dichroism which is related to the reflectivity for right and left circularly polarized light by R± ^Re-*.Since one expects the anyon material to break into domains, the averaged nonreciprocal optical effect will be zero. The distribution width a of the values of is related to the circular dichroism of a single domain 0o by o~-od/s, where d is the domain size and s is the beam size. Lyon et al. reported a nonzero value for a that increased from the noise level ( -25 /irad) at 300 K to -250 //rad as the temperature was lowered.In this paper we present data taken on high-quality YBa2Cu3<>7 (YBCO) films which indicate no measurable nonreciprocal effect. Using a modified fiber gyroscope we have been able to measure nonreciprocal phase shifts with high sensitivity while simultaneously rejecting all reciprocal effects. The phase shift we measure is AQ> sss 27rl(n + -n-)/X, where n+ and n-are the indices of refraction for circularly polarized light of the same handedness propagating in opposite directions through the sample. Equivalently /*+ and n-could refer to the two circular components of a single beam of linearly polarized light, in which case AO is related to the Faraday rotation angle 0 by...

Using single-target off-axis sputter deposition, high quality superconducting films of YBa2Cu3O7−δ were made in situ. These films have properties which are distinctly different from those of bulk ceramics and of post-deposition annealed films. Their superconducting resistive transitions remain sharp regardless of the value of Tc between 75 and 86 K. Normal-state conductivities are as high or higher than the best single crystals. Critical current densities as high as 6×107 A/cm2 at 4.2 K. Tc (R=0) falls off with film thickness down to 10 K for 35–40 Å films. All of the above properties are relatively insensitive to compositional variation. The results can be explained if the in situ growth results in well-formed CuO2 planes with defects occurring elsewhere.

YBa(2)Cu(3)O(7) films have been grown epitaxially on SrTiO(3) (100) and LaAlO(3) (100) substrates with nearly pure a-axis orientation and with transition temperature T(c) (R = 0) of 85 K. A unique feature of these films is their smooth surface. These smooth surfaces enable the growth of short-period superlattices with well-defined modulations. The films are untwinned and the grains grow with their c-axis along one of two perpendicular directions on the substrate ([100] or [010]). The fabrication of sandwich-type Josephson junctions with good characteristics may now be possible because unlike c-axis-oriented films, the superconducting coherence length of these smooth films is appreciably large perpendicular to their surfaces.

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The temperature dependence of the magnetic penetration depth of Bi2Sr2CaCu20g single crystals and YBa2Cii307-s thin films has been measured with a parallel plate resonator technique at microwave frequencies. Both materials show a T 2 temperature dependence between 10 and 25 K, and systematic deviations towards a flatter temperature dependence below 10 K. We have also calculated the real part of the complex conductivity of YBa2Cu307-$ thin films from our penetration depth and surface resistance data and compare them with those of YBa2Cu3C>7-a single crystals.