  In this letter we study finite temperature properties of spin-1/2 interacting
bosons with spin-orbit coupling in two dimensions. When the ground state has
stripe order, we show that thermal fluctuations will first melt the stripe
order and lead to a superfluid of boson pairs if the spin-orbit coupling is
isotropic or nearly isotropic. Such a phase supports fractionalized quantum
vortices. The Kosterlize-Thouless transition from superfluid to normal state is
driven by proliferation of half vortices. When the ground state is a plane wave
state, the transition to normal state is driven by conventional
Kosterlize-Thouless transition. However, the critical temperature will drop to
zero for isotropic spin-orbit coupling.
