  The quantum Hall liquid is a novel state of matter with profound emergent
properties such as fractional charge and statistics. Existence of the quantum
Hall effect requires breaking of the time reversal symmetry caused by an
external magnetic field. In this work, we predict a quantized spin Hall effect
in the absence of any magnetic field, where the intrinsic spin Hall conductance
is quantized in units of $2 \frac{e}{4\pi}$. The degenerate quantum Landau
levels are created by the spin-orbit coupling in conventional semiconductors in
the presence of a strain gradient. This new state of matter has many profound
correlated properties described by a topological field theory.
