Chiral glass: A new equilibrium phase of ceramic high-T-c superconductors

Possible occurrence of an equilibrium thermodynamic phase with a spontaneously broken time-reversal symmetry is studied in a model ceramic superconductor with anisotropic pairing symmetry. It is shown by Monte Carlo simulations that such a ''chiral-glass'' phase is truly stable even under the influence of screening, Existence of frustration in zero external field, arising from the d-wave pairing symmetry of high-T-c superconductors, is essential to realize this phase. Via a finite-size scaling analysis, critical exponents associated with the chiral-glass transition are estimated to be nu(CG) = 1 3 +/- 0.2 and eta(CG) = -0.2 +/- 0.2. These values turn out to be close to those of the Ising spin glass. Phase diagram of the model is constructed and the implications Co experiments are discussed.