  Spin and chirality orderings of a three-dimensional XY spin glass are studied
by extensive Monte Carlo simulations. By calculating an appropriately defined
spin-overlap distribution function, we show that the finite-temperature
chiral-glass transition does not accompany the standard spin-glass order,
giving support to the spin-chirality decoupling picture. Critical behavior of
the chiral-glass transition turns out to be different from that of the Ising
spin glass. The chiral-glass ordered state exhibits a one-step-like peculiar
replica-symmetry breaking.
