Chiral glass: a new equilibrium phase of ceramic high-Tc superconductors

Abstract

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 ν_CG=1.3\pm 0.2 and η_CG=-0.2\pm 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 to experiments are discussed.