  It was proposed that a double quantum dot can be used to be a detector of
spin bias. Electron transport through a double quantum dot is investigated
theoretically when a pure spin bias is applied on two conducting leads
contacted to the quantum dot. It is found that the spin polarization in the
left and right dots may be induced spontaneously while the intra-dot levels are
located within the spin bias window and breaks the left-right symmetry of the
two quantum dots. As a result, a large current emerges. For an open external
circuit an charge bias instead of a charge current will be induced in
equilibrium, which is believed to be measurable according to the current
nanotechnology. This method may provide a practical and whole electrical
approach to detect the spin bias (or the spin current) by measuring the charge
bias or current in a double quantum dot.
